Religion/Faith?

[Joachim]

I have a question: which Black Library novels discuss the transition from the Imperial Truth to the Imperial Cult the most? I sort of ran into the topic while reading "Know no Fear" by Dan Abnett, where it is mentioned from the Ultramarines´ perspective, when confronted to the newfound "religion" of the Word Bearers. I remember that the Horus trilogy also mentions it, characters like Sinderman or obvioulsy Keeler in particular. What other novels go that way? I suppose "The First Heretic" would be of course be among them, but perhaps "The Master of Mankind" as well`?