This is now one of my favorite books. I usually don't read too much fantasy stuff - I usually can't get into it too well. This book was exactly the opposite. I was hooked quickly and the fast pace ensured that I would finish it quickly, also.
Clary seems like a real down-to-Earth character, despite everything that is happening to her (I won't tell you because I don't want to spoil it!). The way she reacts is the way I think I would react if any of this happened to me. All the characters were described really well and had growth in the book.
I would only change one thing, though. Everything would get really exciting, and then slow down dramatically, then get exciting, and slow down again, etc. I think this book would be even more incredible if it didn't slow down so much in between the main events.
Overall, though, this is a great book and if you are debating whether you would like it, you most likely will.