Pretty much a completely different tone from virtually all other WH40K novels, but my favourite series out of everything I’ve read is the Ciaphas Cain series.
Dude who (supposedly) just wants a nice and safe rear echelon job somewhere far away from the battlefronts, keeps ending up in the wrong place at the right time, has to fight his way out to save his own skin, gets mistaken(?) for a hero who deliberately throws himself into the middle of battle to disrupt enemy plots, only for his attempts to use his heroic reputation to get out of the frying pan landing him deeper into the fire, which only grows his reputation further as he somehow manages to save the day (while saving his own skin).
The series’ main gimmick can get a bit repetitive if you binge read the novels one after another, but they’re great as “palate cleanser” reads between more serious series.
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