I don't think anyone could pretend that Douglas Adams' The Hitchhiker's Guide to the Galaxy, which novelizes part of his extraordinarily successful BBC radio series of the same name, ever amounted to much more than a job of media transplant for its author who, having once already told the jokes and the story they engendered, was very likely, at the point he wrote the novel, also preparing to run the whole package through yet another transformation—into a television series, also successful. But whatever form this blatant package comes in, it's a joy.

To begin with, Hitchhiker is indeed a novel about how to travel free around the galaxy; somewhere in between it is a cosmological fable about the construction of our Earth as a gigantic living computer designed to solve the riddle of existence (all costs covered by the creatures who had us built and who manifest...