Ciaphas Cain is back, full of explanations of why all his heroic behavior is really just his being pragmatic and unlucky about things. Really. You believe him, don't you? In this book, he leans rather heavily on the excuse "but it would ruin my reputation if I did that" -- though he does not go into depths on why, exactly, his reputation inspires him to risk his life.
Those who have read the first omnibus will recognize it picks up right after a short story in it, but it stands alone, I think. (Can't really judge since I read this series from beginning to end.) It opens with Cain on-board with the Reclaimers, the super-human soldiers of the Imperium, heading off to deal with a planetary system in revolt against its governor. Cain and Gries, the captain leading the Reclaimers, see that apparent factions were a ruse -- the rebels have set things up to confine them. So they lead missions to eliminate the heavy artillery that would have prevented troops from landing -- Cain being in charge of one because, of course, the Hero of the Imperium would want to lead one. Even with Mira, the daughter of the planetary governor, attaching herself to the mission as the colonel-in-chief of the household regiment. (Governors are aristocrats in this universe, usually.)
Plenty of action and adventure there, but the mission turns up that the rebels are, in fact, genestealers, alien-human hybrids that the tyrannids use in their plots to take over planets. Rooting them only raises the question of where they came from, and Cain finds himself brought along on the hunt for the space hulk that appears to be the source. Mira attaches herself too -- I have to say that I found Cain a little too naive about figuring out her intent. It was too obvious before he twigged.
The story goes on, with action, adventure, the unsettlingly weird space hulk, spaceships stuck together after they materialized in the same location, and Cain, predictably enough, getting into the worst situations by accident and getting out more by luck and love of self-preservation than anything else -- really. He says so. Don't you believe him?