To Say Nothing of the Dog is one of the funniest science fiction books I’ve ever read. It isn’t a silly, knee-slapping romp like The Hitchhiker’s Guide to the Galaxy, but a calmer story that relies more on character interactions than external craziness.
I’m not a huge fan of time travel because of all the paradoxes that are usually ignored or explained away badly. I also watched way too many Star Trek episodes where time travel was used as a fix-it for almost any situation, like some temporal Gorilla Glue.
Fortunately, the books below deal with time travel in intelligent (or just fun) ways, introduce cool ideas, and are generally excellent stories that are very well written.