The topic - the Borgia family - is great, however I just couldn't get into the writing style of this book.
I don't believe I've read anything else by Puzo (just seen the movie!), so I'm not sure if this is his usual style, or if it's because he passed away without finishing the novel. I thought the bulk of it read more like research notes than like a completed story. Events and background material were laid out in a very didactic way, almost like reading a non-fiction history text. That wouldn't be so bad - except that this book doesn't make a large effort to be historically accurate, and some of the events were not at all convincing. I like to be able to at least think, "Well, it MIGHT have happened like that." Instead, I was saying "no way did that happen," to myself.