When people say "Italian Mafia" they think about the "Cosa Nostra",
The "Cosa Nostra" has a single rulebook and a single structure, building up in a pyramid from the soldiers at the base to the boss of bosses at the apex.
In Gomorrah, Saviano writes about "The Neapolitan Camorra", or "The System" as it is known by those on its inside, is a vast, pullulating world of gangs. Gomorrah is an excellent book about the workings of the South Italian Mafia.
This is a book about an Italian Mafia almost nobody talks about, the one concentrated in Naples - The Camorra.
A must read if you want to know more about "The System".