I liked this book more than the first one in the series. It felt like there was more focus on the characters' individual personalities and less focus on trying to make everybody funny. The first book had constant sarcasm and joking from all of the characters. This book felt more balanced. All of the characters were angstier, and some of them were still underdeveloped, but their personalities seemed more distinct.
I do wish that I understood the magic system better. For example, there were portals in the first book that allowed the characters to travel anywhere in an instant. I guess that the portals were rare because there were only two of them in New York, but why can't more be created? Why couldn't a portal be created to bring more Shadowhunters to New York to fight Valentine?
Also, the creepy relationships in this series keep multiplying. The book dropped some very obvious hints that the incestuous relationship won't turn out to be incest, but that wasn't the relationship that creeped me out the most this time. I always get weirded out when a mortal teenager dates an immortal who isn't a teenager. I found Twilight creepy because of this; I found Miss Peregrine's Home For Peculiar Children creepy because of this; I found this book creepy because of this. Age is more than just how you look. Age is life experience and how many years you've been on the planet.
Alec is a teenager. Magnus is 300 years old. Wouldn't a relationship between them be illegal? And what could they possibly have in common that would make them want to date in the first place? The worst part was that when Alec started to tell his parents about the relationship, Magnus knocked him unconscious with magic and then told his parents that he was delusional from demon venom. I actually stared at the book in horror for a minute. What kind of screwed up serial killer behavior is that? Why are none of the other characters concerned about this relationship?
Other than the horrifying relationships, this book was very entertaining. There were twists that I didn't see coming. A lot of action. Some of the more minor characters, like Simon and Alec, became slightly more interesting. I'm looking forward to finding out what happens in the next book.