I am currently writing a thesis on the Italian Mafia...so most of the books are more academically orientated.

I would recommend John Dickie's Cosa Nostra for the most current information and theory on the Mafia.

Other books that are good to read include Octupus by Claire Sterling for a more international perspective on the Mafia.

Excellent Cadavers by Alexander Stille provides a substantial amount of information on the lives of Falcone and Borsellino. There's also a movie based on the book, but it is pretty uniformative and boring.

Men of Dishonor by Pino Arlacchi is the account of the mafioso Antonino Calderone and provides a unique perspective. It is somewhat similar to Tim Shawcross and Martin Young's Men of Honor which is Tommaso Buscetta's confessions. Both provide some good accounts of individual members of the Sicilian Mafia and good description of a number of events. Take their stories as you will-they do offer insight into the Mafia, but both are "pentiti" and have a tendency to portray their enemies in a more negative light than their friends.

Mafia and Mafiosi by Henner Hess is strictly academic-he puts forward a number of theories about what a mafioso is, what the nature of the Mafia is, ect.

Fighting the Mafia and Renewing Sicilian Culture was written by the mayor of Palermo, Leoluco Orlando. It is quite useless if you want to learn about the Mafia and is more self-glorifying than anything, but at the very least you can document some of the changes that have occurred in the last two decades.

Men of Honor was written by Giovanni Falcone, who was above anyone else, instrumental in bringing Mafia information into the public light and the Maxi Trial of the 80s. Most of this information can be found in other books, but its always good to read the primary source.

Fascism and the Mafia by Christopher Duggan is the only book that I know of that covers the time period from the early 1900s to the end of WWII so extensively.

The Allies, Separatism and the Mafia covers a little bit of the Fascist period, but really focuses on the links between the FBI, American Mafia and Sicilian Mafia.

Mafia Brotherhoods by Letizio Paoli gives another good historical overview of the Mafia and the political connections.