The fifth and penultimate book in this series, and I could still read a billion more. Saying that... 
 I was more interested in the sub-plots than the main plot [happens to me with most things I read/watch] and I felt we spent a lot more time with Clary/Jace/Sebastian than we did anywhere else, which disappointed me. And I felt the general tone was a lot more somber, with less of the comedy I had grown to love, as the two most witty and comedic characters [Magnus and Jace] were dealing with love drama and being possessed by a demonic shadow hunter respectively]. While on that topic, I feel like having a 'Jace who is not Jace' for two books is kind of dragging it out. Yes, I know why they did it,and yes, I know the context was different, but still. And as an avid fan of Magnus/Alec's relationship, I really hope they get back together in the next book. 
 Saying all of that, I still absolutely loved the book and reaaaaally don't wanna wait 2 years for the next book!