Obsessed with True Crime discussion

Hello All,
I'm looking for recommendations on the best book that's been written on Gary Heidnik. I've looked over those listed in the Bookshelf, but unfortunately they're really rated there.
Ratings within each respective title didn't prove particularly informative either, as most of the ratings tended to revolve around the reader's inability to stomach the contents.
I try to avoid the more sensationalist publications, with a preference for anything that provides educated insight into development, motives, MO etc.
Any suggestions with these considerations are appreciated.

The only one I have read is Cellar of Horror: The Story of Gary Heidnik. It was very good. I speak as the holder of a degree in English lit who can stomach just about anything.

But you can also count on a good read from Ryan Green, along with the new details that he is always super good at finding and using in his books.