This book is the conclusion to the Isavalta trilogy which begain with A Sorcerer's Treason and continued in The Usurper's Crown. The series is a marvelous piece of world-building, and in the third book we do get to see some new parts of the world, parts which are interesting and quite distinct. In the earlier books, we're treated to a little more explanation of how the magic works; in this book, it's a little bit more "just magic", which is a small disappointment. But we do get glimpses into the unique magic makings of a couple more cultures in Zettel's world.
This book tells a reasonably complete story, but it would be a mistake to try to read it on its own; in fact, I find that my understanding of some of the plot was clouded by the fact that I couldn't remember some details from the earlier books, which I read a fair while back. There is action, excitement, and wonder, and it comes to an ending that satisfactorily wraps up the main story of the book but leaves us feeling that the characters still have interesting, if possibly less epic, lives ahead of them. (As far as I know, Zettel isn't planning more books in the series. The trilogy seems to be fairly well finished, but the world itself is big and lush enough that it could easily hold more novels.) However, Zettel's writing is a little chewier than many of the authors I read, which made this feel like a pretty long book even though it only runs a bit over 400 pages.
It was a good read. I can't put my finger on any real complaints, but it doesn't quite measure up to my memory of the first two in the series. 8 out of 10.