Was having a look in the Waterstones "Young Adults" section for books for my 13-year-old DD (who has said she'd like some surprise books in her Christmas stocking). It can be hard trying to judge how adult a book in the Young Adults section is likely to be because I think there's quite a gap between what I'd think of as suitable for a 13-year-old compared to what I'd think was suitable for (say) a 16-year-old.