This is Book 2 of the Infernal Devices series and it picks up right where Clockwork Angel ended.
It is a fun fast read that is young adult fiction.
I may just stop and wait for all the books to be written in this and the "modern" series The Mortal Instruments. Then, I can start at the beginning and read them all in succession. Maybe not.
The frustrating aspect of these books is that the teen characters are so characteristically teen that I want to slap them up side the head. I just keep thinking, "if they'd only just say what they mean/feel, this could be resolved immediately." But, of course, that doesn't happen in teenager world and it would make the books much shorter to boot.