I don't quite know why, but this book just didn't grab me and I ended up not finishing it. Maybe it's because I'm enough outside the online culture being depicted that it felt both alien and over-explained. Maybe I had too hard a time trying to get inside the protagonist's head.
The basic premise is that a lonely teenage girl, dragged on the run by a mother who has genuinely excellent reasons to want to move invisibly through society, finds illicit friendship and connection through an online chat board (that is, her participation is illicit, not the chat board in general). But the Presence behind the board isn't at all what it seems, and Things Start Happening. If you enjoy imaginative stories about plugged-in culture, you may well like this much more than I did.