Or the guy was half crazy, a pathological liar and liked to brag about things he didn't do, or maybe he was a genius and knew that by "embellishing" reality he could make money, when the regular joe sees a book about a ruthless killer, who killed 300 guys, who killed Hoffa, knows all the secrets about the mob, he buys the book. If it's just another story about a half-assed killer involved in porn and shy, the regular joe is not interested by the story. The same goes for most of the "rat books", you need to be careful about what they say cause they will always brag a little.