Here we have a twisting tale of mystery, magic and revenge. From the get go, it opens like a detective novel, and you know you're not going to get all the answers, until the end. Along the way, we get a good depiction of life in a medieval city, especially how the lower classes survived. In that sense, it was a lot like Oliver Twist, with street urchins and child-thieves running around for scraps.
Unlike the previous books, this one had Sonya staying at the periphery of the events in the story, bobbing in and out with all the characters, and not becoming fully involved until at least three quarters through. As a result, we get to know a lot about the other personages. This was done so well that, at times, it seemed Sonya wasn't even the star of the book.
Also, the authors did a great job in describing the philosophy and effects of magic. The magical rituals were well done, and Areel's charm person spells were so cool. So were the vampire's.
Endithor's execution was of special note: It was one of the most brutal I ever read.
I furthermore felt bad about what happened to Areel; I feel she was a tragic woman driven by vengeance, not an evil person.
The climactic battle at the end was a bit drawn out, but it didn't drag anything down.
One more in this series to go.