The 'Long Earth' is a (possibly infinite) series of parallel worlds, similar to Earth. The "close" worlds are almost identical to 'our' Earth, others differ in greater and greater details, but all share one similarity: on none are there, or have there ever been, human beings. The books will explore the theme of how humanity might develop when freed from resource constraints: one example Pratchett has cited is that wars result from lack of land - what would happen if no shortage of land (or gold or oil or food) existed?[6]
The book deals primarily with the journeys of Joshua, one of the first 'Steppers' and Lobsang, an advanced AI that acquired recognition of rights as a Tibetan motorcycle repairman reincarnated as a drinks machine. The two travellers chart a course to learn as much as possible about the parallel worlds, travelling deep into the "high meggas" as the more distant Earths are named. They encounter evidence of peaceful apelike 'Trolls' able to step at will; of human settlers who learned their gifts early and of aggressive 'elves'. They also encounter warning signs of a great danger deep within the meggas causing catastrophe. The book also deals with the effects of the explosion of available space on the people of the prime Earth 'Datum' and the new colonies and political movements that are spreading in the wake of Step Day.
