I will come back later and put in a better review - but for now, a couple of thoughts. 
 1. I think I liked this one better than the first Mortal Instruments book. Things seemed to happen faster and Tessa, the MC, was not as annoying as I often found Clary to be. 
 2. There were too many similarities between MI and this series - girl finds out about Shadowhunters and Downworlders, meets cute but intensely sarcastic Shadowhunter boy, gets knocked out, ends up at the Institute (run by Shadowhunters), insanely beautiful but snobby girl is there to make our heroine feel inferior, and so on. I think there is enough there in this "world" to make this one stand out more, and not be MI - late 1800s. 
 3. That said, was happy to have Magnus Bane appear, he's always fun. And a lot of the Shadowhunter last names were familiar. I kind of wished that there was a big family tree, but that would be spoilery right now. 
 4. It was a very entertaining read - fast paced and I did like the characters. Had I not read MI, I might have liked this one more. Good setup for the next book.