The Outfit by Gus Russo is an excellent book about the history of Chicago's underworld and how it shaped America
Double-Cross, the biography of Sam Giancana is a great Chiacago Outfit book, it has some mind-blowing information
The Genuine Godfather- about Tony Accardo Chicagos Capo di tutti Capo for about 60 years
Valachi Papers- pretty good book about Stool Pigeon Valachi
Man of Honor-Joe Bonnano is good, has great info about Mafia before it came to America
MAfia Dynasty is excellent