This book is great, but, please, don't exaggerate. It wasn't largely based on facts. There are serious mistakes. It says Marilyn met with Jean Harlow's mom when Jean Harlow's mom was already dead for years. The part of her death IS largely speculation (every theory related to it is this, largely theory). While his investigation about the Kennedys are good, we must take into account he is a big fan of the Kennedys and thus makes his investigation largely biased, which is small problem, something people tend forget. He is also a fan Marilyn, which, believe or not, is also a problem.
I agree with you. I'm not sure if she had anything at all with them, besides being acquaintances. But I don't think they murdered her, or even if she was that important to them, if they had an affair (I would call it a fling on their part). Saying this, I also don't think she was killed by Greenson and/or Murray.
I have that book, but I read it once years ago. It's the only MMB I own since I'm not her biggest fan. I don't know what book is the best since most entertainment medium do not treat her like a real person.