I am a early Bonanno family supporter (you might say a loyalist haha) but i am unbiased when talking about LCN.... Bonanno did break omerta for ego reasons (mainly imo, to clear up the "misinterpreted" Banana war and subsequent retirement/exile.
the book is important because it is source material to verify certain events but many people seem to forget, it was not cool like it is today to admit to being one of the most important people in the drug business. much of the book can be decoded if you have other evidence and can read between the lines.... lastly many people who were associated with Bonanno's NY downfall, were still alive plus why would you want to be associated with Galante, who was publicly murdered just a few years earlier???