This is a great book.
I loved all the interactions between Jace and Clary, as they realize their feelings they have for one another can't go any further because of the fact they are now brother and sister -- not that it takes away how they feel.. just what they want to do about it..
Simon's life becomes a little more complicated as he finds himself being dragged into the shadow world even more so than he would have liked. But, in this case... he has no choice.
There are some things he can't control.
There was plenty of action in this book, and Valentine comes back with a plan in motion. He is a determined man.. even though in this case, they aren't for the better.
More information gets revealed in regards to Clary's mother, Luke and Valentine and you see more of the story that once was.
I would say this book is better than the first.