Raymond Chandler's Phillip Marlowe novels used fictional characters based on Bugsy and Cohen. Chandler was actually around at that time in LA, and always in contact with people who knew the underworld.

James Ellroy is entertaining. He uses a revisionist setting of LA in that era. Very pro-cop, anti-everyone else, especially show biz people but even everyday civilians as well. Ellroy's always thought of LA as being the land of naive idiots. While growing up there, his mother, who he proclaimed to have been an alcoholic and sexually promiscuous, was murdered, so I can understand where he gets the chip on his shoulder. He dissed Chandler when speaking at the recent Noir City festival in LA, and received some boos and hisses. He didn't care.