James Ellroy is a proper writer, but it's unremittingly dark stuff. Even his heroes are usually deeply flawed, he never shies away from showing the worst of human nature. His own early life has clearly had a grave impact - his mother was murdered when he was 8 or 9, and he was little better than a petty criminal himself for a long time.
Matt, you may have seen the film L.A. Confidential, which is based on the Ellroy novel of the same name. The film is very good, but can't capture the genius of the book. As Badger says, his American Underworld trilogy - American Tabloid, The Cold Six Thousand and Blood's a Rover is simply stunning, weaving criminal and police fiction into real events with real people as characters - the assassinations of JFK, RFK and Martin Luther King, the roles of Nixon and Hoover etc etc from the late 50s to the early 70s.
I could imagine these as a long, multi-episode high quality TV series Badger, struggle to squeeze them into films without losing a lot.
A lighter alternative is Carl Hiaasen, who's Florida based crime novels are very funny.
