I used to work for a publishing company and there was an old Italian man who was writing a book that I edited. He grew up in a mob family and his parents friend's were all heavily affiliated too. I don't want to give too many details, but he wrote about some things like Marilyn Monroe's death and JFK's death and a lot of unsolved mob kills, etc. He figured since he was in his 80's and most or all of the people he talked about were now dead, he could write the truth. We finished proofreading and editing the book and made three quick copies with a generic binding and cover to get the final approval. I have one, the head of the publishing company has one, and the writer has one. He decided to scrap the entire thing suddenly. Said he and his family were getting threatened and he didn't care about himself, but he didn't want his children and grandchildren to be harmed.
Anyway, in the book he goes into great detail about the Marilyn death. It was the mob. Hired by JFK. And JFK was getting a bit too big for his britches, so they ended up taking him out as well. Of course, there are a lot more details to it all and I'm not saying a mob member shot JFK, but they were behind the shooting. Fascinating read! The author was a very well known man in his community, intelligent, powerful, used to getting what he wanted (asked me on several occasions to come home with him and made it more like a demand than a question. No I never went), and I have no reason to believe he would make any of this up. I spent months going through family pictures, newspaper articles about him and his family, letters that were saved, etc. For months after he decided to scrap the book I was scared someone would show up at my door and demand the copy I had.
Issues with your story: "asked me on several occasions to come home with him and made it more like a demand than a question. No I never went" Wait, so he's an intelligent, well-connected, dangerous mob man who is entrusting you with dangerous secrets, yet he can't force you to go to his house with him?
"I don't want to give too many details" Why? this is an anonymous reddit account. no mob individual could threaten you if you gave more info.
You've never released your copy, published it, brought its claims to authorities, tried to verify any claims? Why was the man threatened, but not the three individuals who got copies of his book? Where are the other two copies? Why haven't they been released? If it was so dangerous to share these secrets, how are you even alive?
"I have no reason to believe he would make any of this up" You never had any reason to doubt him? Seriously? How are you so easily swayed by mysterious conspiracy theories? You weren't at all skeptical of his claims? Didn't want to investigate for yourself?