Ben Counter soul drinkers series has lots of what you want
he isn't as good a writer as abnett (but then WHO IS), but i remember kinda digging that particular series.
if you haven't read all of abnett's other 40k books you should read those instead though:
Eisenhorn books, Ravenor books, Pariah, Ghosts books + Double Eagle + Titanicus, Brothers of the Snake, Horus Rising, Legion, Know No Fear...those are the must reads, he has done a few other bits and pieces too, including a non-40k generic sci-fi novel called Embedded which is decent