To echo what DC said:
"The Black Book and the Mob" is the definitive work on criminal influence in Nevada gaming. It's a serious, scholarly work, written by Ronald Farrell and Carole Case, both professors at University of Nevada - Las Vegas. You can also find other sources by checking their footnotes and bibliography. If your library doesn't have it, buy it from Amazon or used from Abebooks.com. It's a keeper.

One thing to keep in mind is that Mafia was Johnny-come-lately to Nevada gambling. Jewish gangsters dominated Nevada gaming from 1931, when it was legalized, until the Kefauver and McClellan hearings drove the gangsters underground.