I believe this may be the book, by Brady’s longtime visitor, confidant and chosen heir Dr. Alan Keightly, a theology professor
Apparently it reveals information about the location of Keith Bennett’s body, and also describes Myra Hindley’s involvement in the killings (her being much more a willing and active participant than she claimed)
I heard that Brady did want to release a book with Black Light title, but he may not have been able to. He has limited control of what he can publish, for example he wanted to sue to have the afterword by Peter Sotos removed from his last book, The Gates of Janus, because he hadn’t read it or approved it, but he had no say in the matter
I may be wrong though and perhaps there are two distinct posthumous books
Interesting; I’ve never seen this one before. Can see it’s quite brief - if you’re interested in any further reading I’d recommend these ones: Ian Brady: The Untold Story of the Moors Murders, One of Your Own: The Life and Death of Myra Hindley, Evil Relations (that one was co-written by David Smith) and For the Love of Lesley (which was written by Lesley Ann Downey’s mother) :)