I read them when my little sister got them, just for something to read. XD They're cute, and really well written (plus the illustrations are beautiful). I actually quite enjoyed them, despite being way over the target audience. ^^;
Holly Black has some other books out which definitely aren't suitable for children, but are still really good. I think one's called Tithe and I can't remember the other.
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I would be the laziest girl in the world, but it's too much effort.