This is, like the Gaunt's Ghosts books, a Warhammer 40000 book. I think it's a fix-up. Not just because it's a series of episodes, neatly marked off by the "undertakings" they are about, but because at some points, the characters are info-dumping stuff that we just read in the last episode, albeit very neatly. And I think he was still finding his voice for Priad in the first few stories, but he has the voice down pat for the rest.
Priad is a Space Marine, a superhuman warrior in the far future, and the book opens with a world that summoned an Iron Snake to help it against the horrors of the primuls -- the dark eldar, exceedingly nasty sorts of aliens, who are fond of taking prisoners in order to torture them. We see it all from the POV of characters from that world -- most of it through the eyes of Antoni, the primary clerk who actually sent the message. And having thus been introduced to him, we see the rest of his tale through his eyes.
Though somewhat episodic, it works because it's not unified by the incidence, but by watching the progress and development of Priad. (Which lets him plant a gun on the mantelpiece with greater ease; you aren't looking for it to be significant later, and many of them aren't, but some are.) I think Priad ascends the ranks a little quickly; he becomes a sergeant in the second episode, with only a single story set with him as a low-ranking battle brother. But he has a lot to do as a sergeant. Dealing an evil cult on one planet. Returning to Ithaka, their native planet, for replacements, and finding himself in the middle of a mystery. Doing a new king the honor of attending his coronation and finding that something else was going on. Training young aspirants and finding out that his squad has violated the rules. And leading up to an episode of climatic importance.
A good book.