I like how the conflict with the Strigoi is developing and the interesting clash of viewpoints between the Moroi about how to deal with the problem that this book brings.
I dislike, however, the focus it has on Rose's romantic relationships. The triangle going on between her, Dimitri, and Mason annoyed me, particularly with the acknowledgement from both Rose and Dimitri that a relationship would be a horrible idea because of the danger it would put the two of them in while guarding Lissa. Rose also acts horribly to Tasha, a woman who likes Dimitri, despite liking her before she realized Tasha wanted Dimitri. It was incredibly frustrating to see Rose act like that.
I did really like the introduction of Janine, Rose's mother, and the dynamics of their rocky relationship. I would have preferred more of that and less of the romance.