Heaven's River

The final book in the original ‘trilogy' left things open-ended, with one of the early Bobs having disappeared while off exploring deep space. This book follows up on that, and it is more focused than the first three books as a result. What has happened becomes clear early on, and we're off to the titular setting, which has a resemblance to that of an earlier sci-fi classic (Ringworld). The bulk of the book deals with this, exploring an alien culture that's different from that of humans, but not dramatically so, but where the mystery is how the whole thing has been set up.

Original Bob is the main character here, but there are segments involving other Bobs as they assist him, and a major subplot about a schism within the Bobiverse that is left open for future volumes. (Like The Hitchiker's Guide, ‘trilogy' is becoming an increasingly inaccurate term). There, the focus is on how the Bobs have diverged over what are now 24 generations, and it's not just the antagonists who illustrate this, with others having picked up minor interests of the original and made them the focus of their lives.

But, at least for now, that's background, with the hunt for Bender and the exploration of the alien setting taking up the bulk of the page count. There's inventiveness here, and plenty of action, all of it in the easy-going style that the books favour. It's perhaps difficult to maintain the high pace and freshness of the first book over a set of four, and this is perhaps not quite up to the standard of the preceding three volumes, but it's still effective at finding new things to do without, to my mind, falling into repetition.