Starship Titanic is pretty fun:
Terry Jones wrote it, he of Python fame, but it was fully endorsed by Adams, and Jones even wrote is on the condition that be allowed to do so in the nude.
You could aslo try Adam's Dirk Gently books (of which there are two: Dirk Gently's Holistic Detective Agency and The Long Dark Tea-Time of the Soul). It's about a psychic fat man who solves crimes, really a fun read all round. :3
If you wanted something a bit zany, The Cyberiad by Stanislaw Lem. Same guy that wrote Solaris, only with robot wizards and knights and dragons and tyrants and comedey and complex mathematical ideas. Unless you're into math (which I wasn't) you won't understand a hoot of the mathematical in jokes, but it's still ridiculously funny.