A Cruel and Shocking Act: The Secret History of the Kennedy Assassination doesn't really get to the bottom of it, but it's a great book about the Kennedy assassination, and contains new information (including evidence that Oswald had a CIA handler in Mexico City.)
A few years ago, when I was researching Michele Sindona and Propoganda Due, I stumbled upon a blog that talked extensively about the Kennedy case as well as the Bloomfield files. It also hinted about Montreal being the possible staging area for the assasination (as in Lincoln's case). Back in 2013 I managed to book an appointment to take a look at the Bloomfield files but dropped it because I'm not sure what I might find in the files (although I do believe that the most important parts have been well protected till today and won't be released to the public forever), as even the released docs look interesting (hint: involving Rothchild and Freemansonry).
I've never had more than a passing curiosity about the conspiracy rabbit hole that is the JFK assassination. When I saw recently though someone suggest the possibility that a Secret Service agent may have accidentally hit Kennedy I saw suddenly how that explanation seemed not only to put a lot of the puzzle pieces together (at least the more common quandaries you hear about) but seemed to me plausible as well.
Then again, with all things, it seems impossible they could have covered up something like that without someone leaking/talking.
Well, I guess we will never get into the bottom of the story.