Time: the final frontier. These are the voyages of storytellers throughout the mysteries of time, exploring how to break through its apparently-rigid barriers and break its (apparently equally rigid) rules. But when you think about it, we're all traveling through time together—in what we can perceive as forward. Not all of us pass through at the same subjective rate, of course, because there are teeny-tiny relativistic effects at work, which have to do with our relative motions.

Going into the past–– except in our memories or by inspecting records, artifacts, books, photos and films, etc— has serious ontological and logical ramifications, i.e. paradoxes. That's where the real fun starts; and through the realm of fiction, we're able to travel through time, while scientists attempt to catch up. The best time travel books explore the concept of time travel and show how dangerous and rewarding it can be. What can one ripple in time do?

An example of time tourism, A Sound of Thunder is the source of the phrase, "butterfly effect" because a butterfly dies and the traveler's future is altered. In this thrilling time travel book by science fiction author Ray Bradbury, a hunter is sent on safari sixty million years in the past. All it takes is one wrong step in the prehistoric jungle to stamp out the life of a delicate and harmless butterfly. In the year 2055, greedy entrepreneur Charles Hatton makes a fortune with his company, Time Safari Inc., which allows millionaires to travel back to the prehistoric era to hunt dinosaurs. Strict regulations are in place so that the present is not altered. But, during one time-travel safari, a hunter steps on a butterfly and unleashes a drastic ripple effect through time. Now researcher Dr. Travis Ryer must travel back to prevent the source of the disruption.

Also one of the best sci-fi military books, Slaughterhouse-Five is an anti-war, alien abduction, time travel book (to put it simply). Slaughterhouse-Five is an account of Billy Pilgrim's capture and incarceration by the Germans during the last years of World War II, and scattered throughout the narrative are episodes from Billy's life both before and after the war, and from his travels to the planet Tralfamadore. Billy is able to move both forwards and backwards through his lifetime in an arbitrary cycle of events. Enduring the tedious life of a 1950s optometrist in Ilium, New York, he is the lover of a former pornographic movie star on the planet Tralfamadore and simultaneously an American prisoner of war (POW) in Nazi Germany.

One of the best Isaac Asimov books and a sci-fi masterpiece, this stand-alone novel, The End of Eternity, is a monument of the flowering of science fiction in the 20th century. "The Eternity" of the title is an organization carefully isolated from the rest of the temporal world, staffed by male humans called Eternals recruited from different eras of human history commencing with the 27th century. The Eternals are capable of traveling “up-when” and “down-when” within Eternity and entering the conventional temporal world at almost any point of their choice, apart from a section of the far future which they mysteriously cannot enter. Collectively they form a corps of Platonic guardians who carry out carefully calculated and planned strategic minimum actions, called Reality Changes, within the temporal world to minimize human suffering. As the plot unfolds, the Eternals feel an unspoken collective guilt which causes them to scapegoat the "Technicians" who execute Reality Changes. The Eternals are also troubled that beyond a certain point in the future they are prevented from entering Time. These are the "Hidden Centuries." Beyond the Hidden Centuries they can emerge, but find Earth devoid of human life.

A time travel book that operates sideways in time, Transition deals with parallel worlds and is a variation on the time police theme. Set between the dismantling of the Berlin Wall and the 2008 financial crisis, Transition centers on a shadowy organization called 'The Concern', and how the workings of this organization affect the lives of the novel's multiple narrators and characters. Banks uses the many-worlds interpretation of quantum mechanics theory to imagine "infinitudes" of parallel realities, between which The Concern's agents–known as Transitionaries–can "flit," intervening in events to produce what The Concern sees as beneficial outcomes for that world. Transitioning, or flitting, is only possible for people with a predisposed talent for such movement, who may only flit after ingesting a mysterious drug called 'septus.' When a Transitionary flits into another world, he or she temporarily takes control of the body of an existing inhabitant of that world, along with some of that body's residual idiosyncrasies (such as personality disorders and sexual preferences).

The Forever War by Joe Haldeman crosses the best hard sci-fi books with the concept of time travel. It is a classic science fiction story of William Mandella, a man who is in the top percentile of the world as far as intelligence, education, and physical fitness. As a result, he is included in the elite group of people conscripted into the united armed services of the world to battle the unknown and elusive Tauran aliens. Although this war spans over a millennium, Mandella unwittingly sees it through from beginning to end due to the time differential created by travel through constantly evolving wormholes. Not only is The Forever War an intense, mind-bending space chronicle, it is also a social commentary regarding war, politics, and how executive decisions affect civilians and military personnel alike.

In The Stars My Destination, it is the 25th century where three inner planets of the Solar System and eight satellites farther out are inhabited, and many humans are able to teleport themselves some distance across a planet (though not across space) simply through mental effort. Gulliver "Gully" Foyle was a simple mechanic aboard a spaceship that was attacked by an Outer Satellites raiding party and left a bombed-out hulk. Barely alive, he hailed a passing spaceship but it ignored him, and in his rage he vowed to destroy it and its crew when he got back to civilization. But there was more aboard his own craft than just himself and his dead crew mates, much more, and various powerful interests become interested in his fate, as he educates, strengthens, and trains himself for his mighty revenge. Bester's second science fiction novel, published in 1956, is one of the great classics which inspired scores of other writers and tales.

The Accidental Time Machine follows the story of Matthew Fuller, a research assistant at MIT, who accidentally invents a time machine while attempting to construct a calibrator to measure the relationships between gravity and light. Unfortunately, it will only travel forward, to the future, in ever-increasing intervals of 12 times. On the fifth jump, which sends him forward a few months, he gets arrested for the alleged murder of a drug dealer who actually had a heart attack when he witnessed Matt disappear in his time machine. He is shortly bailed out by someone who can only be from the future, and is left a note urging him to depart in the time machine quickly. He continues forward in time 15 years and upon re-materializing finds that Professor Marsh, his tutor, has taken credit for the time travel invention and subsequently won the Nobel Prize.

11/22/63 is a time travel book by Stephen King about a time traveler who attempts to prevent the assassination of President John Fitzgerald "Jack" Kennedy, which occurred on November 22, 1963. Jake Epping is a thirty-five-year-old high school English teacher in Lisbon Falls, Maine. Jake’s friend Al, who runs the local diner, divulges a secret: his storeroom is a portal to 1958. He enlists Jake on an insane—and insanely possible—mission to try to prevent the Kennedy assassination. So begins Jake’s new life as George Amberson and his new world of Elvis and JFK, of big American cars and sock hops, of a troubled loner named Lee Harvey Oswald, and a beautiful high school librarian named Sadie Dunhill, who becomes the love of Jake’s life—a life that transgresses all the normal rules of time.

Hyperion takes place in the 28th century and humanity has spread across the galaxy, first aboard "Hawking drive" ships and then through "farcasters," which permit nearly instantaneous travel between them regardless of the distances. The farcaster network (the "WorldWeb") is the infrastructural and economical basis of the Hegemony of Man and thus determines the whole culture and society. Also flowing across these portals are the structures of the datasphere (a network reminiscent of the Internet in design, but far more advanced). Inseparable from mankind's technologies is the powerful, knowledgeable, and utterly inscrutable TechnoCore, the vast agglomeration of millions of AIs who run almost every piece of high technology of mankind. The unthinking hubris of man resulted in the death of the home-world (Earth)—which was consumed by an artificial black hole running out of control—and this arrogant philosophy was carried forth to the stars, for centuries.

In Doomsday Book, Willis imagines a near future (first introduced in her 1982 story Fire Watch) in which historians conduct field work by traveling into the past as observers. The research is conducted at the University of Oxford in England in the late-21st century. In the fictional universe, history resists time travel which would cause the past to be altered by preventing visits to certain places or times. Typically the machine used for time travel will refuse to function, rendering the trip impossible. In other cases "slippage", a shift in the exact time target, occurs. The time traveler arrives at the nearest place-and-time suitable for preventing a paradox; variance can be anything from five minutes to five years. Some periods theoretically accessible can also be deemed too dangerous for the historians by the authorities controlling time travel.

This engaging and creatively written novel takes a unique approach to the time travel book. In The Time Traveler’s Wife, time travel is actually linked to a recently discovered medical disorder, called “Chrono Displacement” disorder. One of the main characters, Henry DeTamble, has this strange condition, and as a result sometimes travels to the past and the future involuntarily. Henry is married to Clare Abshire, an artist, and the couple lives in Chicago, where Henry works as a librarian.

In one of Henry’s most significant time travel episodes, which occurs in his 40s, he finds himself in the time of Clare’s childhood. As a result, Clare first sees Henry when she is six years old and he is decades older. She always remembers his appearance, and knows him when she sees him again at the age of 20, when he is only 28.

Outlander is a sprawling time travel book with a romantic context. The protagonist, Claire Randall, is able to travel in time. It is World War II, and Claire is an English nurse vacationing with her husband in Scotland. When she travels through time she engages in an affair with someone else, and has many different challenging experiences and adventures. Claire’s time travel is at first accidental, and is facilitated by touching a special boulder in the magical Scottish highlands. When she first does so, she is thrown back in time and her adventures begin. The author ensures that the book has a great deal of realism with regard to setting and dialects.

First published in 1895, The Time Machine is a classic work of fiction. It is also an integral work of the science fiction genre specifically. H.G. Wells actually invented the idea of the “time machine” in this novel.

In The Time Machine, the distant future is discovered to be extremely bleak for humans and the earth itself. At one point in the future, the world is inhabited by a strange society called the Eloi, as well as bizarre and menacing creatures. When in the world of the Eloi, the time traveler’s time machine is taken, and he must struggle to get it back. He manages to find the machine, and travels further forward in time, eventually reaching a horrifying point where the earth is dying and humans no longer exist.