Catch-22 is Joseph Heller's seminal work. It is about a pilot during World War II, stationed just off of Italy. The basic premise is that he wants to go home, but his superiors continually work against him, making it impossible.
The book is hilarious, especially the first half. It is a biting critique of beauracracy and unchecked capitalism. Every superior officer in the book demonstrates the arbitrariness of beauracratic leadership. Milo in particular is a great example of capitalism gone bad.
The characters are diverse and interesting. From Major Major Major Major who just wants to fit in, to Orr, who likes to do boring things to make the time seem longer.
Yossarian himself is a very likable protagonist, even if he is insane in his own way.