I mostly thought the plot was a little cliche and the characters terribly shallow and American. You can tell this is an old book, because a lot of the stuff that happens simply wouldn't nowadays. Now the book isn't terribly old but still. It's one of LJ Smith's first works, and I've read some of the newer stuff (Night World series) and that was so much better.
I didn't kind the characters too much, but Faye and Cassie were kinda annoying. My favourite character would have been Nick or Diana. Diana simply because she was nice and clever, and Nick because he was the outsider of the inside group.
All in all I think the book was okay, it had some flaws but it was a quick read so I didn't really mind.