What defines multiverse science fiction varies and can often be convoluted, but generally speaking it is referring to a multiplicity of universes branching out into many different moments in time. As complicated as that may sound, don't worry too much because the best multiverse science fiction books contain very little real science. Instead, they create compelling alternate universes and parallel worlds that do more important things as far as fiction is concerned — serve the story.
We are taken into alternate versions of reality and parallel Earths, and many of these great works of art test the bounds of science fiction. Sometimes these worlds remind us of our own, and through them we can glean useful lessons we may be able to apply in one way or another. Now, if you're looking only for the very best multiverse science fiction books, venture no further, as I've compiled the best of the best below.
The Man in the High Castle by Philip K. Dick
In Phillip K. Dick's haunting The Man in the High Castle, America has lost WWII, and now the American territory is controlled by both the Nazi's and Imperial Japan. However, there is an underground novel going around depicting an alternate reality, a parallel universe where America won the war. The book is considered the most dangerous thing in the entire Third Reich, and they will do anything to locate its author and kill and imprison those who have read it.
Dick has written an eerie tale about life and history as it relates to authentic and manufactured realities, easily one of the scariest multiverse science fiction books.
Brasyl by Ian McDonald
Past, present, and future Brazil are all part of the complex narrative in one of the best multiverse science fiction books of all time. It houses three different story lines and sets of characters that will all eventually converge in strange and thrilling ways.
Edson is a self-made talent agent who has risen from the slums to become incredibly rich. Marcelina is an ambitious Rio TV producer looking for a big hit to make her industry calling card. Father Luis is a Jesuit missionary sent into the 18th century to locate and kill a disgraced priest. The three are linked together across time, space, and reality in an insanely ambitious story that begs to be read.
The Number of the Beast by Robert A. Heinlein
The Number of the Beast is structured as a series of diary entries by each of its four main characters. The four travel in programmer Zebadiah's modified air car, to worlds both near and far. The novel's universe contains six dimensions; the three spatial dimensions known to the real world, and three time dimensions.
The four travel through space and time, to both worlds real and imagined in one of the best multiverse science fiction books. It's complex in terms of the thought put into the worlds by the author, but it's essentially about two men and two women on a time machine safari through a plethora of universes.
In War Times by Kathleen Ann Goonan
In War Times is an alternate reality novel with a bit of historical fiction mixed in. But, however you look at it, it's one of the best multiverse science fiction books in recent memory. Sam Dance is a young soldier in 1941 when his older brother, Keenan, is killed at Pearl Harbor. Sam vows to do anything to stop the war, and when he is noticed for his knack of science, he is reassigned.
He starts training in code breaking, electronics, and physics. The big question one of the alternate reality tale asks is this: can technology be prevented from doing as much evil as good?
The Gods Themselves by Isaac Asimov
Of course sci-fi pioneer Isaac Asimov crafted one of the best multiverse science fiction books of the century: The Gods Themselves. In the story, an outcast Earth scientist, a rebellious alien inhabitant of a dying planet, and a lunar-born human sense the imminent destruction of the Sun. Unfortunately for them, and the rest of the planet, nobody will listen!
Humans and aliens team up together across multiple universes in the hopes of saving planet Earth. There are some political insights here, some well ahead of its time, mostly dealing with our massive use of energy.
The Long Earth by Terry Pratchett and Stephen Baxter
The Long Earth is about a series of parallel Earths with doorways leading to adventure, excitement, and the unknown. It's the first of the wildly successful Long Earth series, and it deals with two friends who are trying to learn as much as possible about the parallel worlds.
By traveling millions of steps away from the original Earth, they encounter evidence of other humanoid species and humans living on settlements in other universes. It's incredibly imaginative and one of the best multiverse science fiction books ever written.
Timeline by Michael Crichton
A group of history students travel to 14th-century France to rescue their professor in this classic from Michael Crichton. While still remaining compulsively readable, Timeline addresses quantum mechanics and multiverse theory.
While it's a novel about time travel, it does not subscribe to many notions of other books like it. Crichton suggests that other universes exist, including alternate versions of our own, at the same time as ours, each existing in another time and place, meaning it is possible to access them. Throw in a compelling rescue story and you've got one of the best multiverse science fiction books by one of our most beloved authors.
The Fold by Peter Clines
At first, the reader thinks the incredible technology at the core of the story is actually teleportation. However, as the mystery unfolds, we learn that the government doesn't actually teleport anyone — they are sent to an alternate universe.
The mystery unspools further after we find out that it's all a part of a secret government project. And, not to give too much away, the alternate universe is one much darker and deadly than ours. The tense atmosphere of a tight page turner makes this one of the most readable multiverse science fiction books of the 00s.
A Darker Shade of Magic by V.E. Schwab
Schwab’s concept of parallel universes, each containing a different version of London, is an interesting jumping off point for one of the best multiverse science fiction books you'll read in ages. There are "travelers” who serve as liaisons between the parallel cities, smuggling artifacts from one to the other.
If you are a fan of magic and sci-fi page turners, pick this on up as it's among the lighter reads in terms of subject matter. The fast paced bouncing between worlds is both endlessly imaginative and a joy to read.
The Gunslinger (Dark Tower #1) by Stephen King
Lastly, lets end on the novel that launched one of the most epic multiverse science fiction series of all time: The Gunslinger. The Gunslinger is the first book in the Dark Tower series, widely considered King's magnum opus. Here King introduces his most enigmatic hero, Roland Deschain of Gilead, the Last Gunslinger.
Pursuing the notorious man in black (an evil being who can bring the dead back to life), Roland is a decent man who seems to bring destruction wherever he goes. Through the series we follow him across alternate universes on incredible adventures, but nobody can deny the book that started it all is among the greatest multiverse science fiction books of all time.