Hmm...there are many of those. There is all of Discworld, Good Omens, Dirk Gently (I actually find Gently books funnier than Hitchhiker's Guide), there was one huge edition of Monolith almanac (#5) that was solely dedicated to humorous fantasy/SF/horror, and then there is a whole pile of regional satirists that I grew up with.
But overall, I'm a very sympathetic reader and I will often laugh with a joke in a book or at a very funny/witty phrase. Which can pose a problem when, for example, one is reading The Once and Future King on a train. Luckily, I live in a metropolis, where odder sights can be seen daily on the commute, so I get mostly overlooked.
Recently, I've been laughing along with Rivers of London and, surprisingly, Kyogoku Natsuhiko's Kyōgokudō series. On the surface, it doesn't seem very humorous, but there is both unintentional (by the characters) hilariousness and snark flying back and forth.