If you're into crime novels, I'd strongly recommend two by George V. Higgins: "The Friends of Eddie Coyle" and "The Digger's Game," two of the best ever. If you're after non-fiction crime books, try "Little Man - Meyer Lansky and the Gangster Life" by Robert Lacey, and "The Black Book and the Mob" by Ronald A. Farrell and Carole Case, which gives a splendid history of gambling in Nevada and Mob influence in the industry.