Of course, now we'll have to wonder if he was collaborating with Kerry, or if he just claims that
Personally, I have my doubts Kerry Thornley was much involved. He was dealing with paranoia for about the last 10 years of his life, and cut off associations with just about everyone. His old friend Robert Anton Wilson said that Thornley became convinced Wilson was with the CIA, and for a while Wilson himself had a mild fear that when he left his home Thornley might be there to attack him out of deluded self-preservation.
Thornley's paranoia may have begun with Jim Garrison's investigation of the connection between Thornley and John F. Kennedy's assassin (or supposed assassin) Lee Harvey Oswald. Or it may have begun earlier, for apparently Thornley, Oswald and a few others who were in the U. S. Marines together were subjects in some type of military experiment involving brain-affecting chemicals. (Adam Gorightly wrote about this in The Prankster and the Conspiracy
, which is where much of this post is from. I'm writing from memory, so may be a little off on a couple details).
In any case, Thornley became increasingly incoherent. I once heard him rant in the very late 1980s or very early 1990s, and he talked about having a warehouse full of information on various conspiracies. He then asked a reporter what year he was born; when the reporter told him, Thornley said, "You'll be dead in three years, probably by fire." He sounded completely serious, whereas Thornley in his right mind apparently always had a sense of tongue-in-cheek about him.
During those last years, Thornley traveled here and there and would suddenly disappear, sometimes living on the street or with whoever was willing to deal with his mental illness, for which he refused treatment. Apparently, that's a common problem among those suffering from what they call or used to call (I'm not a psychologist, so don't know for sure) paranoid schizophrenia--if you're paranoid, you're likely to think the doctor is out to get you. He then had several medical problems and ended up getting regular dialysis after suffering kidney failure.
All in all, it seems unlikely he trusted anyone enough during those last years to work on a book with em.