Hitman: The Untold Story of Johnny Martorano: Whitey Bulger's Enforcer and the Most Feared Gangster in the Underworld by Howie Carr. This was a well researched and written account of Martorano's life. He was more of a business partner of Bulger's who killed heaps of people than a hitman or enforcer. Keeps you on the edge of your seat describing all the mayhem of the Boston underworld in the 60s and 70s.