I am pleasantly surprised by how much I liked this. This is the first of Clare's books that I've read, not having jumped on the Mortal Intruments bandwagon. I thought that the steam punk elements would add a certain flavor and I was right.
Tessa is a bit of an enigma, while she certainly has the damsel in distress syndrome, I will allow most of her behavior to being thrust into a world which she was previously ignorant of. At the same time, though, she is not a doormat and I liked that she sometimes saves herself despite being thrown into circumstances and events well out of her league. She makes mostly the right decisions and her loyalty to her brother shows her strength of will and determination. This most certainly made her a stronger character and much more interesting. I really enjoyed all the manners of creatures we see here, the 'Downworlders' and the world building is thorough and richly well rounded.
As for the two boys front and center, Will and Jem, both impressed me and are different enough that I really wasn't bothered by the perceived love triangle in the making. Their close relationship is not often seen in YA and the fact that they care so much for each other gives that aspect of the story more depth of feeling.
There are just enough (so many) questions left at the end that I am eager to read the next in the series.