I have never read any of Stephen Baxter, and now want to try some...I have read almost all of Terry Pratchett however, and this book shows echoes of subjects he has been mulling over for many years; like in Dark side of the sun, there are many worlds and many different sorts of intelligences; like in Thief of Time, time and space do not behave in a linear fashion; as is the case in Lords and Ladies, other intelligences are inimical to humans and can use 'soft places' to journey to our world; as in Science of the Discworld I, II and III, the nature of parallel universes branching off at multiple points until they become an infinity, a multiverse, is explored...
Joshua Valiennté is not the first child to 'step' into the Long Earth on Step Day, but he is the calmest, and ends up leading the others, frightened, disorientated and hurt, back to safety on 'our' Earth. It turns out he is a natural stepper, so is a shoo in when there is a project to step as far as possible beyond the known Earths, into what is known as the High Meggers, perhaps a million or so steps away from what becomes known as Datum Earth. Accompanying him on this journey into the unknown is Lobsang, an AI entity who claims to be human in that he is a reincarnation of a Tibetan mechanic...the ideas spark off so continuously you feel other authors might build several volumes from the most castaway of terms, but here there is a lightness of touch that belies the seriousness of intent.