I was under-impressed by the first Seanan McGuire book I read, the YA series novel Beneath the Sugar Sky, but still prepared to be wowed by this more adult outing. I'm sorry to say that didn't happen.
McGuire's prose is perfectly functional, and at times very effective. But even the best lines tend to fall by the wayside, run over by sardonic asides and displays of Attitude before they have a chance to flourish. At times, the entire book feels like a collection of asides. In deadly peril while saving your loved ones? No no reason not to mix in a throwaway comment about flower arranging or baking or whatever it may be. In short, I felt the central adventure missed out on much of the adventuring because McGuire was so intent on showing us how cool the narrator is.
Our hero suffers, unfortunately, from Good Guy Arrogance - a condition in which the good guys (because they are Good Guys) can do anything they want, and it's okay, whereas Bad Guys are castigated for the same behaviour. To choose the easiest example, in a book about how Toby's estranged daughter has been cruelly and wickedly kidnapped. causing all sorts of pain and harm, Toby ... kidnaps someone. But it's okay, because she and her cohort have Good Intentions. High-handed doesn't even begin to cover it. This isn't a flaw unique to McGuire, of course; Good Guys have been kidnapping, torturing, and stealing for a long time. But in this more enlightened age, I'd hope for better.
McGuire also makes a continued point that Toby continues to put herself and others in danger because,... well, that's just the way she is, but she's plucky and adorable, so everyone forgives her. To me, that's not much different from the pulp era he-man putting his love interest in a safe place to wring her hands while he goes off to Fight Evil. Neither one should be appealing now. I'm all for strong, plucky characters, but adorable doesn't excuse poor choices any more than protective does.
This is a late volume in a long series, so there's a lot of backstory. McGuire does a decent job of working that in without trying to cover everything that's gone before. At the same time, she goes far deeper into mythology and worldbuilding than seems warranted. It seemed every page required naming a New Kind of Fae and describing its powers, to the point that I wanted the Dungeon Master to just give us a run down of the creatures first. An early reference table in the book that could have served that function, mostly just gives us pronunciation.
Finally, the book is intensely political, to the extent that it recalled Ursula Le Guin's comments about Katherine Kurtz. That is, it's not (mainly) a reference to current politics, but to Machiaveliian machinations. For me, at least the result was tiresome and tedious.
Unfortunately, 'tiresome and tedious' largely sums up my response to the novel as a whole. It's a shame, because there's some good writing here, and a carefully conceived world. However, (as with Beneath a Sugar Sky), I felt the whole effort could have benefited from subtlety and depth. I can't see reading another book in the series.
The book throws in a bonus novella, but it largely retells some aspects of the story from the point of view of Toby's kidnapped daughter. I didn't feel it added much.