People either love or hate Terry Prachett. His Discword series is up to 30 plus books and is one of the best worldwide selling series in history. Few books have made me laugh outloud as these books. The last ten or so are more serious, which the first ten are more goofy. You really should start from the beginning but if you want to jump in the middle I'd start with either Hogfather or Going Postal.
Discworld - Wikipedia, the free encyclopedia
Discworld - Wikipedia, the free encyclopedia