First of all, it took me about three hours to get through this book. That's short even by my standards.
The good: Continues where Firestorm left off, lots of action, and an overall well-paced read. There was little lag time, and Ms. Caine makes her characters very interesting. I actually care about them. We got some cute backstories, more info on Venna (Alice, the Djinn), and the final reunion of Joanne with the Wardens (the constant on the run from everyone including her former employers was getting a bit old). The idea was fresh, at least to me, in that chunks of the story were told from the point of view of memories; it was a creative idea. The Sarah storyline was handled in an interesting manner, I'm curious how it plays out later on. It kind of came from nowhere, but provided an intriguing twist.
The mediocre: There are times where I scratch my head and go "huh?" at some of the events in this book (and others in the series). The "evil twin" concept didn't work too well for me, it just feels cliche. The storytelling keeps this from being too much of a negative, though.
The bad: There is always a bad, and in this case it's that Ms. Caine is falling into the LK Hamilton mode of deus ex machina. How convenient that the now-deceased Imara is the new Earth Oracle. How convenient that this results in Joanne getting Earth Warden powers at just the right time. How convenient that she is now the second most powerful person in the world. And how convenient that the Djinn who like her break away from the Djinn who mostly do not. It's things like this which bug me. Does Joanne need more powers? She is a take-no-grief character who started out as a Weather Warden, died, became a Djinn, was reborn, gained Fire Warden abilities, has several Djinn actively assisting her at every turn, and is now an Earth Warden, making her only the second triple-threat to exist. I hope Joanne doesn't go the way of Anita Blake and find new powers in every book. She doesn't need them, she is an amazing character all on her own.