I've been interested in studying organized crime, mainly pertaining to Italian-Americans, and am hoping to find some book(s) on the topic.
The Five Families by Selwyn Raab is very good at covering the history of the New York Mafia families.
The Complete Idiot's Guide To The Mafia by Jerry Capeci is excellent when it comes to the overall history of the American Mafia, and busts many myths that have surrounded its origins and activities.