There is no reason she could not write her own book, although she did state on her blog that she was not writing a book. Our writing perspectives and styles are very different. I go with the straight ahead matter of fact approach to the overall investigation and history of the case, while Joy tended to focus on victims and the emotional appeal of the case. Not saying one way is right or wrong, because ultimately that is determined by the reader, and by history. We just have different styles and objectives.
And again, I'll reiterate that the need for the book was rooted in the fact that no one was listening to what was being found. Not the reporters, not Stearns, and not Joy. Yes, the notes pretty clearly pointed to Heinrich as the likely perp in Jared's case as well as Jacob's, and I twice suggested Heinrich to her as the perp, per the Hart notes and conversations with Larry Peart. She was zeroed in and Hart and the media followed suit. Based on the feedback fr Stearns it appeared they were zeroed in on Rassier.
The huge problem with emotional attachments is that it tends to lead the beholder in a single direction and kind of a tunnel vision approach. People see what they want to see and they let their emotional involvement affect and direct their processing of information. We've seen it several times in this case.