The woman who said Blue Rose before her death
Honestly, unless confirmed or partially hinted in the show, at this point I consider the book completely irrelevant (maybe I'll change my mind when the final dossier will come out). Albert says the names and Windom Earle is not in it, that's it for me.
It's definitely been hinted at in the show and sort of confirmed by Frost that it is relevant.
In any case, I feel the books (being written by one of the writers) helps enrich the story and gives an indication into the thinking process and background story.