And he said he would quit during their conversation at the bar. She also knew that this particular case consumed his mind since 80.
So she made an executive decision not to tell him directly, but put it in her book instead.
"You want to hide something from a nikka? Put it in a book" - Jadakiss
Maybe Hays figures it all out if he read his wife's book when she was still around
Maybe, maybe not.
I'm a researcher and writer by trade, so maybe this is a little different for me, but consuming information is not the same as processing it, which itself doesn't necessarily lead to useful interpretation.
From my point of view, it may have been that it didn't necessarily matter if Wayne had read the book before 2015. He was wedded to a certain interpretation of events (murder, possible pedophile ring) that really ruled out an interpretation of events that didn't involve grotesque violence and/or corruption. Essentially, Wayne and Amelia were working on parallel tracks that never intersected during the 35 years that they lived together (and after they dropped the case for their own safety/marriage, those tracks could never intersect). And even when he started working on the case in 2015, he was still wedded to the lurid interpretation of events as much as he had been wedded to Amelia.
He could have read that book 10,000 times and never really figured it out at that point. He needed the openness that came from having some sort of closure, even if it was a false closure, to read and interpret the case in a different way. Junius's story, and the fact that it was in many ways
completely different from what they had expected, opened him up to new possibilities in the case. Only in that moment was he really able to allow his and Amelia's tracks to intersect, read the book, and get anything significant from it.
So yeah, for me, all these people who are saying that Wayne could have solved the case if he just read the book don't really have a firm grasp of how research and interpretation actually works. shyt, Amelia's ghost even tells you what's happening during her monologue in that scene.