|Author||Terry Pratchett & Stephen Baxter|
|Cover artist||Rich Shailer|
|Series||The Long Earth|
|19 June 2012|
|Media type||Print (hardcover & paperback)|
|Followed by||The Long War|
The "Long Earth" is a (possibly infinite) series of parallel worlds that are similar to Earth, which can be reached by using an inexpensive device called a "Stepper" – designs for which are one day posted online suddenly allowing humanity to explore worlds "East" and "West" of "Datum Earth". The worlds are mostly familiar, though others differ in greater and greater details, but all share one similarity: on none are there, or have there ever been, Homo sapiens – although the same cannot be said of earlier hominid species, especially Homo habilis.
The book deals primarily with the journey of Joshua Valienté (a natural "Stepper") and Lobsang, who claims to be a Tibetan motorcycle repairman reincarnated as an artificial intelligence. The two chart a course to learn as much as possible about the parallel worlds, travelling millions of steps away from the original Earth. They encounter evidence of other humanoid species (referred to as trolls and elves); of human settlers who learned their gifts early – including Sally Linsay, daughter of the inventor of the stepper, who joins them on their expedition; and of an extinct race of bipedal dinosaur descendants. They also encounter warning signs of a great danger, millions of worlds away from Earth, causing catastrophe as it moves. The book also deals with the effects of the explosion of available space on the people of Datum Earth and the new colonies and political movements that are spreading throughout the Long Earth.
A young girl, Helen Green, and her family (with the exception of her brother, Rod, who is unable to step) trek across the long earth to form a new community, Reboot, on Earth West 101,754.
After stepping across "The Gap" – a universe around two million steps from the Datum where the Earth no longer exists – Joshua and Lobsang encounter the threat that has caused the slow migration of Trolls away from the gap. First Person Singular is a being that absorbs other sentient life forms, eventually taking over everything on earth before stepping to the next. It currently cannot pass The Gap. Lobsang elects to stay in First Person Singular's universe and commune with it, in the hopes of convincing it not to advance further, or at least to not absorb all other sentients.
Joshua and Sally return to Datum Earth back the way they came. Upon reaching Earth West 101,754, they hear news that Datum Madison has been destroyed in a nuclear explosion, the result of a bomb planted by a terrorist group of humans incapable of stepping (called "phobics" in the book's terminology). The book ends with the two of them briefly seeing the explosion site, before retreating to Earth West 1 Madison, where a backed-up instantiation of Lobsang contacts Joshua by phone.
Reviewing the book in The Guardian, Adam Roberts found it to be "much more like a Baxter novel than a Pratchett one." It was also said to be "a charming, absorbing and somehow spacious piece of imagineering."
Sequels of the novel in the series are: