I just wrote my review of this novel's prequel, The Wizard Hunters, based around the premise that these books are more complex than they seem. Just as this book goes more in depth into the complexity, so I'll continue, in this review.
As I said, on the surface, these books are simply a great swashbuckling sort of adventure (quite YA-friendly, I might add; there's sex but it's fade-to-black, and the violence is realistic but not excessively gory), but it's the characters that make it worth following. And all of them are complex and rich and believable, even the unnamed ones who get a throwaway line in a background scene.
This book gives us a great deal more insight into Tremaine Valiarde, our intrepid heroine. It gives her a love interest, for one-- but a marriage of political expediency, and with a wonderful Wellsian twist: the husband is from a matriarchy and assumes that she will be the authority figure in the relationship. It's a fascinating logic experiment that yields phenomenal results of characterization.
And this book contains the scene I love to use as an example of what Strong Female Characters ought to be, but never get to be: HUMAN. Tremaine is primarily a human character. She's set up to be a neurotic, bloody-minded person. In this book, she is presented with a desperate situation that catapults her into a leadership role she doesn't particularly want but knows she must take-- to secure it, she has to play a life-or-death game of chicken, and she does so with iron nerves, but believable irritability. (Over the course of about fifty pages there's a delightful little thread of consistency as she bites off each of her nails one by one, followed up later when her husband notices her doing the last one; in many of the scenes she otherwise seems utterly unmoved by the most horrifying things, but if you pay attention to her hands, you can see she's just shredded internally.) And later, she is presented with a choice: murder in cold blood to secure just a bare chance of saving not just her friends but probably her entire world, or spare an innocent man's life and ensure the death of everyone she loves?
The most important part of this is that unlike in many works of fiction, Tremaine doesn't just murder someone, feel on-screen guilt about it, and then move on. No, she returns to think of her hapless victim in tiny little realistic moments of self-doubt and post-trauma for the rest of the series; you know fine well that in the fictonal future, she still remembers the man she shot in cold blood to get a truck.
Like a real person would.
She's not some action superman. She's ruthless because she has no choice. She's her father's daughter, even if she doesn't understand him. And that's possibly the crowning touch to the whole little arc of characterization: she is continuing the same arc her father was on in Death of the Necromancer, when he overheard Inspector Ronsarde and Doctor Halle discussing him. Even then it is apparent; they think him some sort of cold-blooded psychopath, but in his moment of doubt, he knows he is only doing what he has had to do to survive.
Not just any author could make a connection like that, but that is how three-dimensional these characters are.