For this list, we will take a look at 100 of the best science fiction books of all time. These 100 works were chosen for their historical significance, their legendary status as classics, their interesting subject matter within the genre, and their entertainment value. Pure fantasy novels such as “Lord of the Rings,” were omitted from this list. Fantasy is sometimes included as science fiction due to the fictional species and alternative sciences of magic found in the stories.
For this list, we will stick to a basic definition of science fiction. The stories must include some concept of real science and how it may be applied in the future, fictional scientific ideas and theories, imagined future science and technology, or major environmental changes. Science fiction stories can take place at any time period and on earth, on alien worlds or nearly anywhere the author decides to take us.
While this is a list of the 100 best science fiction books, we will not be giving a definitive ranking among the 100. Each of these books is great for different reasons. It would be near impossible to make a call on one of these books being better than the next. One may be more historically significant while another may appeal more to readers due to the relatable characters. Who can say what criteria makes one truly better than the next for individual readers?
Science fiction challenges the reader to contemplate serious topics. These topics can range from ethics and morality to the meaning of life and what it is to be human. They can challenge us to move boldly towards a future of innovation. Many inventions were first imagined on the pages of a science fiction novel. Indeed, science fiction has not just predicted future technologies but has also directly inspired them.
This genre captures the imagination like no other. It can also work as a cautionary tale of what the future may be like if we do not heed the author’s particular warnings. Science is fun and exciting, but technologies can also be used for evil as well as good. Last of all, science fiction is just plain old fun. It sparks the imagination and takes you to whole new worlds. Without further ado, here are 100 of the greatest science fiction books of all time.
Mary Shelley’s “Frankenstein,” was published in 1818, making it one of the oldest books on this list. This timeless masterpiece is considered a classic in two genres. It’s a staple in the collection of science-fiction fans as well as lovers of horror. It deals with ethics in science and what happens when mankind goes too far from ambition and curiosity.
Some of the best science fiction takes a look at the possible future and how it could be negatively affected by technology. “Nineteen Eighty-Four,” tells of a dystopian future where government lies and propaganda rule the day. Few books have had such an impact on the culture and psyche of the human race as this still-relevant, cautionary tale by Orwell.
“Dune,” is just one of many novels on this list that have been adapted for the silver screen. This epic space saga is filled with political intrigue, mysticism and adventure. Herbert created a coherent and complex universe for this grand space opera to take place in.
This seminal work by H.G. Wells is the foundation and inspiration for almost every time-traveling story since 1895. It tells the story of a time traveler who goes to the future to find a world in ruin. There is no advanced society, only a dying planet, war and a mysterious race called the Morlocks.
“War of the Worlds,” was one of the first science-fiction books to deal with the concept of alien invasions. It set a high bar for all of the invasion novels and movies that would follow. Orson Welles’ 1938 radio presentation of this story was said to have caused mass panic from listeners who believed it to be a newscast.
Huxley weaves a fascinating tale of a utopian future that isn’t as great as it seems. Things seem to run perfectly thanks to genetic manipulation, a heavy dose of medication and a caste system that no one can escape from.
Jules Verne was, in many ways, ahead of his time. His adventure stories and early science-fiction works seemingly predicted many future inventions and technological achievements. This novel tells the tale of Captain Nemo in his fantastic submarine, the Nautilus. The ship is surprisingly modern considering the 1870 publishing date of this book.
This is one of Jules Verne’s more fantastic stories. A German professor, Otto Lidenbrock, discovers a passage into the center of the planet. Along with his nephew, he discovers an amazing underground world inhabited by prehistoric creatures.
Asimov describes the complex nature of mankind’s relationship with his own creations. This novel affected an entire generation’s idea of what robots are and what they could be. Tropes and concepts from this novel still show up in modern-day works of science fiction.
Author Kurt Vonnegut survived the WWII bombing of Dresden by hiding in a slaughterhouse. This was the clear inspiration for the title of his seminal novel. This strange tale follows Billy Pilgrim as he experiences his life in a non-linear way after contact with aliens.
This masterpiece of science fiction explores deep concepts such as determinism, fate and how history often repeats itself. The book won the Hugo Award for Best All-Time Series and should be on every science-fiction fan’s to-read-list.
Many people are more familiar with the film directed by Stanley Kubrick than they are of this novel. That’s unfortunate, because it’s a must-read for science-fiction fans. It explores the mysterious origins of the human race and their place in the universe.
Instead of Martians invading earth, this is a collection of tales about humans traveling to and colonizing our closet neighboring planet.
This is Ray Bradbury’s version of the totalitarian, dystopian future. If you’re a fan of “Brave New World,” and “Nineteen Eighty-Four,” this novel will be right up your alley.
Only one human is left alive in the future. He is surrounded by bloodthirsty vampires and must struggle to survive. This story has one of the best twist endings in all of science fiction.
This novel tells the story of a bleak future filled with ignorance after a nuclear disaster puts mankind back in the dark ages. This work explores how bad things can get when science is vilified.
This story features a stranger that doesn’t look so strange at first glance. Valentine Michael Smith was raised on an alien world and now must reconnect with the people of earth. This novel explores age-old questions about which is more important, nature or nurture.
“Solaris,” is both science fiction and a psychological thriller. A scientist studying an alien ocean must confront his own deep-buried memories. What is causing him to suddenly see a dead lover from his past?
This novel is another on our list that has been translated successfully to film directed by Stanley Kubrick. Alex is consumed with violence until an experimental fix does away with his base desires. This book is dripping with dark comedy and satirical social commentary.
Science fiction is often thought provoking and makes us question the morality of how and when scientific advances should be used. This novel by Daniel Keyes is a great example of this. In this tale, a developmentally disabled man is offered a treatment to change him into a genius.
This cult classic is one of the best science-fiction comedies of all time. It’s smart, funny and filled with social commentary in a way that will make you laugh as much as it makes you think. Arthur Dent goes on an adventure with an oddball cast of characters once the earth is demolished to make room for an intergalactic highway.
This novel is a timeless children’s book that is an enjoyable read for all ages. Meg and Charles are two children who go on a trip through time, space and other dimensions to find their missing father. One part science fiction and one part fantasy, this tale deals with some heavy themes such as religion, family and the value of individuality.
This is another science-fiction story that deals with ethical questions of science and the concept of playing god and messing with ecosystems. If you enjoyed the big budget, blockbuster movie, do yourself a favor and read the novel by Michael Crichton.
Few people have done as much to popularize science as Carl Sagan. Sagan was an astronomer, astrophysicist and cosmologist. This novel by Sagan explores what it might be like for humanity to come into contact with a more advanced alien species.
This novel is groundbreaking for its thought provoking look at issues of gender and feminism. The book was first published in 1969, making it ahead of its time in tackling some tough subjects. On the planet of Ekumen, there lives an alien colony that has no set genders.
This novel may seem more like fantasy than science fiction due to its use of dragons, a royal family and other fantasy tropes. It is, however, set on an alien world with no shortage of science-fiction technology and concepts.
This long novel comes from Stephen King, the master of horror. It has elements of horror as well as fantasy. The science fiction elements come in the form of an influenza strain that was developed for use in biological warfare. Good and evil collide in a post-apocalyptic world.
War is a popular topic within science fiction. “The Forever War,” deals with the topic masterfully. far off in outer space, young women and men are drafted into an intergalactic war. Upon returning to earth, the soldiers barely recognize their own home planet. Written towards the end of the Vietnam conflict, this novel is still relevant today.
Koontz does here what he does best with a story of shady government institutions and questionable uses of science and technology. This early work by Koontz tackles the subject of unchecked genetic manipulation.
Dan Simmon’s weaves a tale of pilgrims on a journey to a far away planet. A mysterious being called the Shrike may be able to provide the answers they seek. This science fiction adventure is based on the “Canterbury Tales,” by Chaucer.
“The Children of Men,” was written in 1992 and is set in the near future of 2021. In this mysterious science fiction story, humanity hasn’t seen a real live birth in a decade. This novel offers some top-notch world building. This leads to a believable story even with the fantastic plot elements.
Like the previous entry on this list, “The Hunger Games,” succeeds due to fantastic world building by the author. This is a well thought out universe. In a dystopian future, contestants are chosen for a contest where they must fight for their lives to survive. The initial book was followed by a whole series that is well worth reading.
This is science fiction meets the zombie apocalypse genre. The trend continues to move zombies away from the supernatural creatures of horror that the once were. In this novel, like so many other modern zombie tales, the creatures are the result of science and technology gone awry.
This novel has often been likened to the movie “Castaway.” Instead of being stranded on an island, the protagonist is stranded on the planet Mars. This story presents the triumph of the human mind and spirit, even in the most dire of situations. It also presents some realistic science and space-travel scenarios for a work of fiction.
This is science-fiction comedy at its best. Redshirts is a term that references the TV and movie series, Star Trek. Lower ranked crew who wore red shirts on those shows often never made it back from their adventures. In this comedic story, a new starship crew member realizes that his colleagues seem to die at an alarming rate.
This story involves a caste system in the future where most things are color-coded to fit into their designed niche. The protagonist, Darrow, is a lowly “red,” and does manually labor in the mines of Mars to make the planet habitable. Once he realizes that his work is in vain, he starts to question things.
This is a brilliant novel that deals with artificial intelligence and what it means to be human. Like so many other science-fiction books, it asks tough questions about the ethics of science and mankind’s responsibility to our own creations. It was the basis of the cult-classic film, “Blade Runner.”
Ender was genetically created to be a genius hero for earth. Believing himself to be playing a simulation game, Ender finds himself in the middle of a real war with an alien force bent on the destruction of the human race. This novel kicked off a series of books as well as a movie adaptation.
This may be the quintessential work of cyberpunk science fiction. A hacker is hired to take control of a virtual-reality network called the Matrix. Does that sound familiar? This book took on the topic of virtual reality way back in 1984.
40. Exo by Fonda Lee
This thoughtful story explores what it means to be under rule of a foreign power and what peace is really worth. In this novel, the world has been colonized by an alien race, The humans and this invading species have been coexisting peacefully for a century.
Vonnegut explores the consequences of the bombing on Hiroshima to end WWII, but he does so in his own distinct way. This is not a book set during the actual events, but a story of a man named John who wishes to write a book about those events.
Imperialism and patriotism are taken to task in this biting commentary on the military-industrial complex of a future where citizenship is earned by military service. Multiple bug-like alien species band together to assault the human race. Earth is attacked and humans are violently torn limb from limb as they mount a counter attack, but who are the real invaders?
This is an interesting take on a future human society that lives on both the earth and the moon. Libertarian ideology is explored in this story of a revolt from moon colonies against being ruled over by earth.
An alien invasion leads to decades of utopia on earth, but at what cost? This is another science fiction look at what may happen if the human species is confronted by a superior, more advanced species. It comes from the same author that gave us “2001: A Space Odyssey.”
Buck Rogers was one of the first space-explorer heroes to capture the imagination of children and adults alike. The imaginative designs for creatures, spacecraft, technology and alien landscapes inspired generations of science-fiction comics, movies and literature.
Like the previous entry on our list, this is another compilation book that collects comic strips. Flash Gordon debuted six years after Buck Roger’s first appearance in 1928. The stories and artwork set the bar for science-fiction designs for decades and inspired future sci-fi works such as Star Wars.
This entry may seem strange to science-fiction fans, but hear me out. Keep in mind that this list is for the best books and not just novels, therefore a comic-book could qualify. This single issue introduced Superman to the world in 1938. This story about an alien with super-human powers was written by two teenagers from Cleveland, Ohio.
Superman’s origin story created an entire sub-genre of science fiction that is still massively popular in comics, TV and film today. Obviously, one can no longer purchase the single issue unless they’re a millionaire, but you can still read it in a compilation book titled: “Superman: The Golden Age Vol. 1.”
While Superman popularized the idea of heroes with powers, the graphic novel, “Watchmen,” deconstructs the idea of superheroes and deals with complex political and moral ideas. This graphic novel is often cited as a turning point in the perception of comic books as serious literature.
This unique novel is a mix of science fiction, techno thriller and historical fiction. It deals with a group of WWII-era code breakers and a second group of decoders from the 1990s. Historical figures from Winston Churchill to Ronald Reagan show up in this complex drama. Concepts such as digital-monetary systems and cryptography are explores in realistic detail.
A father and his son must travel across a decimated America in this post apocalyptic tale. The story is filled with the usual dangers of such a situation including roving bands of desperate thieves and marauders. This is a story with a lot of heart that explores the power of love as well as the darker side of humanity.
The Saga is actually a collection of novels that mix the genres of science fiction and fantasy. In this universe, there are humans and creatures of magic that can create rifts to connect distant planets.
This is both a science fiction story and a love story. It deals with a man who has an odd problem. He randomly jumps through time. His loving wife must learn to cope with his frequent disappearances and unpredictable reappearances throughout her linear timeline.
This science fiction war novel follows the military career of a soldier named John Perry of the Colonial Defense Forces. The novel is filled with great world building, creative technologies and a slew of interesting alien races.
This award-winning science-fiction novel tells the story of a mysterious alien object racing toward our sun. People from all over the solar system are concerned, and a ship is sent out to investigate the matter. This is one of Clarke’s best science-fiction masterpieces.
The twin planets of Urras and Anarres have vastly different political and economic systems. One is a capitalist society that struggles with inequality. The other is an anarchist’s and socialist’s dream utopia. The main character is a scientist named Shevek who accidentally starts a revolution.
Great science fiction novels often inspire movie adaptations. In this case, the Star Wars film franchise came first and inspired these novels. Many novels came after “Return of the Jedi.” These kept the franchise alive during the gap between the original film trilogy and the modern movies. The best books of the bunch were the three novels that became known as “The Thrawn Trilogy.”
Ray Bradbury is a true legend among science fiction authors. “The Illustrated Man,” is a collection of 18 different short stories. Common themes pop up in most of the stories such as human psychology and the sterile coldness of technology.
This 1992 novel is an epic space opera. It deals with themes such as love, betrayal, human relationships and genocide. It’s also filled with imaginative alien races and technology. Superhuman intelligence and variable physics are explores as well.
Asimov shows up as the author on this list quite a few times. This is for good reason. He believed that science fiction can be combined with any other genre in literature. Here, Asimov combines science fiction with an old-fashioned detective story. far into earth’s future, hyperspace travel has been conquered and planets are being colonized.
“The Mars Triligy,” is often considered to be Kim Stanley Robinson’s crowing achievement. This is actually a collection of three novels that were titled: “Red Mars,” “Green Mars,” and “Blue Mars.” The main theme is the colonization of Mars. These novels span over 200 years and detail the earth’s political structure, technology and social issues connected to the colonization.
This book won both the Nebula and Hugo awards. Kivrin is a young lady who is studying past ages of humanity. She gets stuck in time at a particularly dark period and becomes an unlikely source of hope as her peers struggle to rescue her.
This is a dark and unique tale of an eccentric scientist working on some unusual research. The book takes place in the city of New Crobuzon which is built within the remains of an ancient beast. The scientist, Isaac, has an encounter with a bird-like alien that will change his life forever.
C.S. Lewis is well known for his fantasy novels featuring a certain lion named Aslan. What is less known is that he also penned some fascinating science fiction. “The Space Trilogy,” is about a philologist by the name of Elwin Ransom. Upon journeying to Mars, Ransom finds out that Earth has been exiled from the rest of the solar system.
Red Schuhart and his friend Kirill travel into the Zone to salvage things left behind by aliens. A robust black market exists around these alien artifacts. The Zone starts dominating Red’s life and he journeys back there again and again to find the answers that he seeks.
Four different versions of one person from alternate dimensions meet in this witty science-fiction novel. This book is a classic among feminist literature and a fascinating piece of science fiction that delves into the concept of gender roles.
A woman in her 30s is able to communicate with the future. Connie can specifically connect to the year 2137. The warnings from the future have serious relevancy for today, but of course Connie is simply deemed insane by current-day society.
This story is notable for its unique and realistic characters. It is set on a vulnerable space station and during a war. It’s not about fantastic technology or alien races, but instead takes a more real-world look at what a space station might be like. Then, it creates a suspenseful story set in this well-designed world.
This is another science-fiction work that deals with virtual reality. It was turned into a big-budget, special-effects extravaganza film directed by none other than Steven Spielberg. The novel tells of a utopian virtual reality known as the Oasis. This book is known for its fun inclusion of a ton of pop-culture and video-game references.
In the future, earth is in shambles due to environmental issues. New hope arises when a stargate is discovered right in our very solar system. It’s a mystery who built the doorway in the first place, but it quickly leads to humans colonizing planets outside of the solar system and discovering other intelligent species.
A virus nearly wipes out an earth colony on the planet Jeep. Only a few women survive the ordeal. After generations of change and adaptation, the humans lose touch with the roots of their humanity, until some fellow Earthlings arrive on the planet.
When a proud alien race has its home planet destroyed, they must learn to coexist with another race on their new, adopted world. The task of preserving their race may come at the expense of losing their very culture and identity.
There is often debate on what is the earliest work of science fiction. This book certainly has a strong case for it. Written in 1666, this is the oldest work to make it on this list. This is a feminist masterpiece from a time when you would hardly expect such a thing. A woman is stranded on another world and becomes its leader. She uses her new power to get rid of war and sexual discrimination.
This novel is both science fiction and a police procedural. It takes the unique concept of two cities that actually occupy the same space, and it combines this with a good old murder mystery.
Kaye Lang is a biologist with a disturbing theory. She believes that long-gone diseases are coded into human DNA. Worse still is that they could potentially be brought back into the world to reek havoc on the human population. When a virus hunter discovers a new strain, she fears that her theory has become a reality.
Time, space and physics are no longer making any sense after a mysterious disaster plagues the town of Bellona. This novel has a very “Twilight Zone,” feel to it, as weird occurrences bewilder the people of Bellona. Two moons appear in the sky, buildings are damaged only to reappear intact and time is no longer consistent.
This book contains 12 short stories that revolve around one central theme. In this sci-fi world, the human race has turned into the Human Galactic Empire. Throughout a hundred millennia, humans used four pillars of science to spread throughout the cosmos. However, the fifth science ended the flourishes empire for good!
“The Fifth Science” explores the aftermath of humankind’s collapse. The stories all take place after the burgeoning empire’s downfall, covering a wide range of themes. Every story is unique. However, they all reflect the dangers and pitfalls of human ambition.
- Available in digital and paperback formats
- 336 pages
- Compilation of 12 stories
- Multiple themes and genres
This novel from the creator of Tarzan is one in a whole series about the hero named John Carter. Carter is a Civil War-era soldier who finds himself on Mars. He ends up as a sort of “reverse Superman,” being an alien on another planet who then becomes a powerful hero. A Disney movie was made about John Carter that didn’t fare too well at the box office. That’s unfortunate, because this novel is a brilliant piece of science fiction.
This novel is like a mix of a Sherlock Holmes mystery within a science-fiction setting. It features one of the bets twist ending on this list of books. Mike Erikson has unique gifts and is asked to travel across country to investigate a device discovered by DARPA scientists that can fold dimensions.
This is a science-fiction thriller and detective story rolled into one. The heroine, Shannon Moss, works for Naval Criminal Investigative Service. Shannon must come to terms with her past as she searches for a missing girl in this tale of time travel, mystery and military intrigue.
Charles Yu weaves a science-fiction story that explores the father and son relationship. It also deals with the themes of life, linear time, human memories and how we create an identity for ourselves.
Kady awakes one morning with nothing on her mind besides her relationship with Ezra. That same day, the earth is invaded by aliens. This book deals with war, large corporations and how they often profit from those wars with little thought about the consequences to the little guy caught in the middle.
Detective stories and mysteries keep popping up in this list of science fiction. This is yet another one that brilliantly blends the two genres. In a world preparing for an near-future asteroid impact on earth, a detective must work to solve a murder mystery. The death has been officially ruled as a suicide, but the detective suspects foul play.
Part of the old United States is now a militaristic republic, perpetually at war. June is a young genius from an elite, wealthy family. She is being trained for military service in the republic. Her world is changed forever when she runs into Day, a young criminal who was born into poverty.
Margaret Atwood’s brand of science fiction is sometimes called “speculative fiction.” She might even be called a futurist. This is someone who looks at trends in politics, culture and especially technology. They then try to predict what the future may hold. To some degree, most science-fiction authors do this. In “Oryx and Crake,” Arnold has crafted a romantic adventure.
This is a cautionary tale about the dependence people have on technology, especially being connected to the internet. In a future South Africa, a teacher realizes something is wrong with the kids she knows. They seem more caught up than usual with their online lives.
In the year 2380, an Commonwealth is developed to connect multiple worlds. They span 400 light years and are all connected via wormholes. When a distant star mysteriously vanishes, a ship is sent out to investigate the anomaly.
Renata Ghali travels deep into the stars in search of a planet that is free of war and poverty. The planet was seen in a vision by Lee Suh-Mi. It may even hold the answers to the origin of earth and life on our planet. This novel deals with the idea of keeping secrets and the consequences that can stem from it.
Aliens discover an enormous object that is dubbed the artifact. Everyone is apprehensive about encountering the race that could have built such a massive, technological wonder. Two humans and a band of exotic alien explorers seek out answers to this mystery in the fun adventure.
This 1979 novel was the first in an epic series called the “Canopus in Argos,” series. Shikasta is also known as Colonized Planet 5. The book uses the structure of a history lesson filled with documents, research papers and journal entries to describe a planet that is actually the earth from the viewpoint of others.
A small girl named Rose is riding her bike when she falls down a shaft. The rescuers are met with an alarming discovery. She seems to be in the grasp of a giant metal hand. This is an intriguing thriller that will keep you engaged til the end.
An odd band of Hollywood stars and actors roam the now-decimated Great Lakes region. This tale is set in the future after the collapse of civilization as we know it. The survivors are willing to risk everything for art and the human race.
The author of this science-fiction tale is a real-life scientist. Specifically, she’s a biologist. This is perhaps why she is so good at creating realistic and fascinating alien species. This is a story of an inter-species conflict set in a realistic, well-crafted fictional universe.
The Confederation is a government of numerous alien worlds and species. They have granted the people of earth a membership in this group, but it’s not for free. While the Confederation has evolved past war and violent conflicts for themselves, they enlist the aid of humans to fight such battles for them as the entry fee for their Confederation citizenship.
“The First Encounter” is the first novel of the “Ascension Wars” series. It offers a riveting start to a more significant tale. Filled with iconic science fiction themes, the book delves into the possibilities of space colonization and what mysteries lie beyond our planet.
In this story, the fictional United Nations of Earth set a ship out to colonize a nearby planet. Upon arrival 90 years later, the ship’s inhabitants find that a thriving alien species already inhabit their target planet. The ship’s captain must figure out what these aliens are and make tough decisions that could impact all of humankind.
- Available in digital, paperback, audiobook, and audio CD formats
- 359 pages
- USA Today bestseller
- The first book in a series
This is not just a great story, but a great example of unique story telling. The city of Veniss is explored through the eyes of three different characters. These vastly different people each have a unique voice and perspective on things.
In “The Last Melody,” you’re taken to a not-so-distance future where humankind has become a spacefaring race. Interplanetary democracy keeps the peace among colonies. Meanwhile, advances in biomedical research and technology have extended human life expectancy by several decades.
While investigating a series of grisly murders, our main character uncovers a massive conspiracy that threatens the way of life for billions!
This story plays out like a mystery thriller novel. Elements of action keep you on your toes as you continue to dive deeper into this futuristic tale. With artificial intelligence and human survival themes, this novel has plenty of captivating moments to keep you enthralled.
- Available in digital and paperback formats
- 410 pages
- Broken into three acts
- Science fiction thriller
This novel has been previously published with the title: “Story of Your Life.” It was latter turned into the movie, “Arrival,” which ultimately lead to the book-title change. This book takes a realistic look at how a first contact with aliens might go down.
This is a collection of science-fiction short stories from award-winning author, Ted Chiang. The stories hit on a number of subjects such as portals into other dimensions, artificial intelligence and alien scientists. They all contain realistic and relatable characters that make the stories really resonate with readers.
This novel by Gene Wolf consistently ranks high on lists for both science fiction and fantasy books. It uses many fantasy tropes but is set in the future, millions of years from now. All that we know of history and culture is a distant, long-forgotten memory in this new fantastic world.
This is a destruction-of-earth story. The planet’s last survivors struggle to survive as they drift off among the stars. A new planet is found that offers hope for future generations. Unfortunately, it also offers plenty of dangers and obstacles that must first be overcome.
Science fiction is one of the most fascinating genres in all of literature. It’s a diverse and exciting genre that has spawned countless sub-genres of its own. It is one of the earliest forms of fiction. This can be witnessed in this very list that contains books from as far back as 350 years ago. Science fiction forces us to take a serious look at humanity, technology and the good and bad that can flow from scientific discoveries. It can be fun and adventurous, funny, or deep and thought provoking. No matter what type of stories you enjoy, there should be plenty of books on this list to entertain you.