It's an absolutely superb TV show, it's an original dramatic serialisation of a non-fiction book that was written about ten years ago called Gomorrah. The book was written by an Italian journalist about the Camorra, a criminal fraternity somewhat similar to the Sicilian mafia but it originates from Naples and the Campania region of southern Italy.
They are extremely violent and successful drug traffickers (one of the biggest Camorra bosses in the 2000s, Paolo di Laoro, was pulling in around 250 million euros a year), but they are much more fragmeneted into small clans than Sicilian or American mafia families.
The name Gomorrah is a word-play on Camorra and of course the biblical cities of sin, Sodom and Gomorrah. It's well-worth checking out. The cinematography is absolutely amazing (though of course since the days of Breaking Bad that is kind-of expected now for a prestige drama)
[video="youtube;-4QORgagblU"]https://www.youtube.com/watch?v=-4QORgagblU[/video]