If you, like me, can't wait for Clockwork Princess to come out, you might want to check this snippet Cassandra posted on her tumblr.
Warning: I don't think the snippet is a spoiler but if you don't want to read anything from or about the book before it comes out please stay away from this post. :)
"Tessa craned her head back to look at Will. “You know that feeling,” she said, “when you are reading a book, and you know that it is going to be a tragedy; you can feel the cold and darkness coming, see the net drawing tight around the characters who live and breathe on the pages. But you are tied to the story as if being dragged behind a carriage and you cannot let go or turn the course aside.” His blue eyes were dark with understanding — of course Will would understand — and she hurried on. “I feel now as if the same is happening, only not to characters on a page but to my own beloved friends and companions. I do not want to sit by while tragedy comes for us. I would turn it aside, only I struggle to discover how that might be done.”
“You fear for Jem,” Will said.
“Yes,” she said. “And I fear for you, too.”
“No,” Will said, hoarsely. “Don’t waste that on me, Tess.”
You ca find this snippet at : Cassandra Clare Tumblr.