A good funny book for me has to include most of the following: silly, but not over the top, set-piece scenes; a witty, seamless blend of the high- and low-brow; some degree of satire or parody; and liberal use of sarcasm and/or irony. (Side note: Great Simpsons quote — Comic Book Guy: "A sarcasm detector? That's a real useful device.) Rarely does any book include all of these elements, because if it did, it'd be a spaghetti-thrown-at-the-wall, choice-less mess. So, allow me to explain what I think to be the three different categories of "funny" novel.
1) Funny characters: Character-driven novels are my favorites! I love "watching" bumbling, silly characters who can't seem to get out of their own ways engage in all sorts of misadventures. In these novels, the plot and writing have to have some semblance of funny, but it all hinges on the one or two main characters committing acts of dumbassery and nonsense. The best example I've come across is Switters, Tom Robbins' depraved CIA agent in Fierce Invalids Home From Hot Climates. Switters, a lothario in every sense of the word (he even seduces a nun!) travels the globe, hilariously expounding on everything from technology to religion to linguistics to the evils of advertising. I wouldn't necessarily want to have a beer with Switters, but I'd definitely pay to see his stand-up comedy routine! Another, perhaps more familiar, character is Ignatius Reilly in John Kennedy O'Toole's A Confederacy of Dunces. Ignatius, an overweight sometimes-hot dog vendor who lives with his mother, spends several hundred humorous pages navigating his way through the various absurdities of life in New Orleans. Purpose for earlier Comic Book guy quote: Doesn't Ignatius Reilly have to be the basis for the Comic Book Guy character on The Simpsons???
2) Funny plot: Here I'm thinking about books that are funny on a scene-by-scene basis, or novels themselves that are framed around a ridiculous and/or hilarious premise. This is probably the most common type of funny novel. Most representative of this type, and probably most widely read, is Joseph Heller's classic war satire Catch-22. Kurt Vonnegut's Slaugherhouse-Five is another classic that fits this bill. I loved both of these novels! Though a bit more obscure, since it's one of his lesser known novels, Richard Russo's Straight Man is an absolutely hysterical skewering of academia. Have you heard that old joke: Why are arguments in academia so fierce? Because there's nothing at stake. (Hmm...that probably translates better verbally.) Anyway, Straight Man also includes one of the funniest scenes I've ever read — involving the main character, a professor at a small college in Pennsylvania donning a fake nose and glasses, and threatening on live TV to murder one duck per day from the university's pond until he gets his budget.
3) Funny writing: These novels make you laugh on a line-by-line, paragraph-by-paragraph basis, whether or not the plot even hangs together or the characters are the least bit memorable. The conversation starts and stops here with David Foster Wallace. Yes, Infinite Jest, is difficult, disturbing and sad, but the novel also includes some of the best funny writing ever included between two covers. I'm also a huge fan of DFW's essay collections — his writing on everything from the Adult Video News Awards to his experiences on a cruise are the standard by which all sarcastic, high-brow/low-brow-blend writing should be judged. I still get a little misty eyed thinking about the fact that he's no longer with us.... Anyway, in this category, I'd also toss in Junot Diaz' The Brief Wondrous Life of Oscar Wao. The blend of Spanish and English euphemisms and deeply funny dialogue make this book as memorable as it is fun to read.
(I suppose I could add a fourth category: Unintentionally funny. This would include general writing, scenes, or entire novels that are so stupidly awful they're funny. Hello, Dan Brown!)
I'm sure there are hundreds and hundreds more examples, so what am I missing here? What are your favorite funny novels?