Just finished reading Betrayer.
Oh. My. God. Possibly the best Warhammer 40k book I have ever read. Aaron Dembski-Bowden really is at the top of his game, and as much as I enjoyed First Heretic, this is even better. I literally could not put the book down, it was epic from cover to cover and literally oozed authentic atmosphere. The main characters and Primarchs were perfectly portrayed, I literally cannot find a single thing to criticize about it.
9/10.