Definitely the best Warhammer novel I've read up to now. It tells the story of the titular Imperial Guard Commissar Ciaphas Cain. In contrast to what one would normally expect from a commissar, he's not a vainglorious headcase shooting troopers for minor infractions left and right. In fact, he's quite likeable. Just a guy who'd really like a quiet posting as far away from the shooting as possible. And failing pretty hard at that.

The books are written in the style of his memoirs. He doesn't think overly much of himself, but somehow got himself into some heroic situations and gathered a reputation for it.

The books a chock-full of likeable and relatable characters, and the author knows how to write an engaging novel.

I don't think it's really a good first Warhammer 40k series though, as it doesn't quite to enough exposition on the setting for that.

Overall, quite a big recommendation from me if you're already familiar with the setting but haven't read the Ciaphas Cain series yet. I'm quite happy right now that there are a lot more books left in the series.