Since you appear to be interested in him, check out the book "Boss of Bosses: Paul Castellano and the FBI". Some of the book is a little "inventive", for lack of a better term, but the overarching storyline of bringing down Big Paul and his cohorts is fundamentally true.

"Gotti" by Capeci is a good read, especially back to back with the Castellano book. Gravano's book is also excellent. These three give a good summation of the Gambinos from the late seventies up to the early nineties.