I'm reading the Knight codex. I think it is well written. Chaos will SO be getting a data-slate, I think. Towards the end of the first section of the book the author talks about Knightly Houses that have fallen to Chaos and Imperial Knights that have become Daemon Knights. So, the background is right there... ripe and ready to be harvested...
PS: Does GW not list individual authors anymore? Not that I'd blame them for stopping after the abuse this community has heaped upon some of them... I don't see an author listed for this codex (of course, I'm still getting used to navigating digital books)...