I'm a huge John Gotti fan, and have read many biographies on him & the history of the Gambino Family. I suggest, Mob Star by Jerry Capeci for a decent biography of Gotti, though it does drag on a little. Mafia Dynasty: The Rise & Fall of the Gambino Crime Family, excellent read, very imformative, written by John Davis who actually met Lucky Lucciano.
Also check out Underboss by Sammy the Bull Gravano, it was a very interesting read and very graphic.
I'm about to read Man of Honor an autobiography of Joseph Bonanno who ran the Bonanno family for years. This book raised a lot of contraversy when it came out in the 80s, Paul Castelano along with other mobsters read it.

From what I understand Henry Hill's biographia is a great read also.