L.A. Confidential by James Ellroy (1990)

Unbelievably complicated and delightfully absorbing tale of corruption in the LAPD in the 1950s. Amazingly adapted into an excellent movie (good work Brian Helgeland!).  See also Big Nowhere, a prequel (sort of) to L.A. Confidential. Excellent story. Evocative portrait of L.A. in the 1950s.