Our buddy Marius ("hero" would be too strong a word) has come home, made up with his pissed-off old flame, and settled down to an honest life with the woman he loves. Of course he is bored crapless. Fortunately, in some sense, the dead rise up and drag the woman he loves away into the underworld. The dead also stab Marius through the chest. This doesn't slow him down like it would most people -- he's got some experience being dead himself -- but it's no way to make friends.
With kidnapping and murder as an opener, matters quickly get desperate, and they stay that way. Marius winds up running around the continent, as he did last book, but this time it's not because he's been shanghai'd into a whimsical quest. He's trying to prevent a disaster -- and it's kind of his fault. And Keth is pissed at him again, and she's not wrong either...
What I find interesting here -- aside from the deft stake-raising from farce to catastrophe -- is that this a distinctly unromantic book. That's unusual in fantasy, and I don't just mean "genre romance is taking over". This is a story where magic will not turn up at the end to make everything right; nor will the gods, the Force, or the force of a happy ending. It's all down on Marius -- and Marius, despite some unusual talents, is not omnipotent. Therefore, not to be spoilery, but the ending is kind of grim. I'd say "realistically grim", but this is a world where the dead get up and walk.
(Oh, gah, I've just made it sound like a zombie apocalypse novel. No. Farthest thing from the author's mind.)
This is also (I'm certain this is the same theme), a distinctly agnostic book. I won't go into details, because that would be spoilery. But I'll say that this might just be a "grand evocation of rationality" in a way that other authors have flailed at.
(What is it about comedy writers that they do humanism so well?)