THE LONG MARS for a reason. The possibilities are infinite. Story and character development are quixotic and secondary. A super race of humans is also postulated, but of course being human means being never completely free of human flaws (in both this and the multiverse of all possible worlds.) So the U.S. must go plant flags on these other alternate worlds, and be jealous of anything living there that isn't us (if more intelligent.) Given that Terry Pratchett is a whimsical fantasy writer who often wears a Gandalf-like hat, (author of GOING POSTAL), and that Stephen Baxter is a hard SF scientist type (who appeals to a different mindset), putting them together in order to iron out the wrinkles each of them possess in attracting audiences (while bending their believability quotient toward the scientific) was a good idea, although it does make this experimental fiction, in a way. Hard SF fans may not cringe at the fantasy elements, and straight fantasy fans may not either, but both may need to compromise. The writing is good, whether tongue in cheek or not, and the narrator (Michael Fenton Stevens) is always engaging, and, at times, superb in his dramatic character voicing.