First part of this book dragged for me just because I didn't like the point of view shift from character to another character. I felt it interrupted the flow the the book, but after about 40% in when the focus seems to linger more with Clary, Jace and Sebastian, I was hooked. Very intense!! 
 Lines are blurred as I wasn't sure who was "good" and who was "evil." 
 (view spoiler)[The couple that breaks-up at the end of the book was a shocker for me. I hate to see that relationship end. (hide spoiler)]