I think Kolbler does a good job of detailing the rise of the Mafia. Italians calling themselves the Black Hand rob and blackmail guilable Italian immigrants. People like Colossimo, and Capone get into the protection busiess. This leads to other rackets, and the Mafia is born. Capone was not a member of the Mafia group, but he knew their main leaders. Capone and before that Torrio become the main influences in the Chicago underworld. This is a detailed biography of Alphonse Capone. The book also shows the corrupt nature of early Chicago politics and the start of Prohibition. Capone because of his leadership qualities and friendship with Torrio becomes a effective leader of the Chicago underworld. Al used whatever he needed to establish his rule. This included blackmail, torture, and murder. He also was generous to those who were loyal to him. There was both a good and dark side to Al Capone. If you betrayed him, then he could beat you to death like the three Sicilians. If you treated him as an equal, he could help and befriend you. Kobler shows all the complexities of Al Capone,  He may have evil traits, but a very real human came through in Kobler's biography. This is a very detailed, but also very readable history of Al Capone
This leads to other rackets, and the Mafia is born