It seems that a lot of people are frustrated by the fact that this book is really about Savannah - not really a true crime book at all. But I don't really think this was ever intended to be a "true crime" book (even if GR crowd sourcing says so.) Yes, there's a crime, but it seemed to me that the point of this book was Savannah, not the murder. The murder seemed to me to be merely the vehicle for discussion of Savannah and the characters there and the way society saw Jim Williams.
I don't usually read true crime books, but if it were the author's intent to write one, I think there would have been much more focus on details, motivations, etc.
So, if you go into this expecting a true crime story, you'll probably be frustrated since that's not really what the book is all about. If you look at this as a book about Savannah and its multiple social structures and quirky residents, you'll probably enjoy it a lot more!