Empire of the Vampire is quite a wild ride with lots of grey characters - which I enjoy reading about because they are so much more real. Gabriel is a very interesting character, and his understanding of faith throughout the book was a major point (even though that isn't really clear at first). There are a lot of moving pieces in this story, but I really like that we stick with Gabriel and his POV instead of jumping from group to group as people separate from him. 
This is a fairly dark story, with lots of death - so be prepared. I had guessed a couple of the big surprises a little early, but the little mysteries of Gabriel's life were very well written.