I just read Gomorrah by Roberto Saviano. I highly recommend it in order to understand all sides of the mafia.

Basically the mafia is a state within the state. It provides for its members and is highly involved with trade just like any other state.

I think a lot of people are attracted to the violent sides of the mafia, but in reality its just as wrong as only focusing only on the military and police side of the United States.

Killings are usually only done when the position of the Mafia as a state or its business interests are challenged.

Gomorrah explains how the mafia in Naples is doing business and it also explains when violence is done. Usually violence is done to keep everything calm. In fact violence is often a sign of weakness from the mafia. Its a sign it feels it position insecure.