Underboss

Salvatore “Sammy the Bull” Gravano is an American gangster. He became the underboss of the Gambino crime family. In this book The Bull relates the events leading up to his helping with the prosecution sentence John Gotti, the crime family's boss. He agreed to testify as a government witness against him. Along with other mobsters in a deal in which he confessed to involvement in 19 murders.

Sammy the Bull has an unbelievable memory. He can recall names and facts about many parts of his life. Which suggests it was Sammy and not Gotti, who was the brains of the Gambino family. He tried running things, quietly and in the ways of Cosa Nostra.

Gravano frequently returns to the theme of living his life based on the rules of Cosa Nostra. You may ask, isn't Gravano hypocritical for talking about Cosa Nostra when he turned into a rat against John Gotti?

One of the best books about the Mafia I've read.