Great sequel!
After all the information given to you in the first book I did find this book a bit drawn out at times. I also found the scene a bit jumpy at one point. But obviously Clare does that so you'll keep reading and wanting to know what happens next. Which I did.
For some reason I found myself wishing that Valentine turned out to be a good guy; probably cause i'd love to see Jace, Clary and Valentine all working as a family... but obviously that's not going to happen. Valentine is obviously evil.
I would've also love to seen Clary and Jace's relationship develop a bit more. And that doesn't really happen until the end. Obviously they're struggling to gain a brother-sister dynamic and it's difficult because they love each other in a romantic way. Am I the only one that wants to see them work out as brother and sister and not romantically? Because I think it's a little strange...
Other then that I loved that Clare brought in Isabel and Alec's parents and little brother. I think they added something interesting to the whole story.
As for the twist of the book - a little heart breaking but not as shocking to me as finding out Clary and Jace were siblings.
Also; I've fallen in love with Luke's character.
Something else that kept me reading was the constant talk about how Valentine had done something special to Jace and Clary and by the end (and in the middle) you find out about Clary but not quite Jace and so I'm still a little confused.
Overall; I still enjoyed the first book a little more but I think this one gives you a lot more to think about and had great action! I'll give it an A-/B+