Okay, my issues with this book are exactly the same issues that I had with the first book. The dialogue seems too modern for the time period and too informal for the class. I can easily put aside my twitchiness (I suspect that might not technically be a word, but as far as I'm concerned, it is) about Gemma's rebellious/girl power nature because her back story allows room for it.
That said, I continue to pretty much love these books. I banged through this one (548 pages) in an afternoon because I didn't want to stop. Both books have just the right combination of fantasy, Gothic creepiness, boarding school trouble, cattiness, mischief, comedy of manners and romance.
The magic system itself is pretty cool--I really like the alternate dimension/world aspect of it. After returning from the Realms, the girls can continue to do magic in our world for only a short amount of time--I think that's an especially nice touch.
I did figure out Circe's identity before it was revealed, but only just barely. The scenes with Pippa were really, really creepy. I'm all excited for the next book! FUN!