Johnny
I believe the Kennedy assassination has the most books written about an historical event. Do a search. There are JFK books pertaining to a Cuban connection with Castro, the mob, the CIA, the FBI, doctors in on the conspiracy, etc. Name the angle and there is probably a theory in a book somewhere. Off the top of my head, I know one "Destiny Betrayed: JFK and the Mafia."

Another excellent one is "Best Evidence," but it does NOT have a mob connection.