Also try reading "La Cosa Nostra" by John Dickie Interesting read on the History of the Sicilain Mafia,Explains how they formed and tells you about the First Known Hit on record,not finished book but good up to yet Hope this helps.
The Mafia Is Not Primarily An Organisation Of Murderers. First And Foremost,The Mafia Is Made Up Of Thieves. It Is Driven By Greed And Controlled By Fear.
Between The Law And The Mafia, The Law Is Not The Most To Be Feared
"What if the Mafia were not an organization but a widespread Sicilian attitude of hostility towards the law?"
Hope this helps.