Attanasio is one of speculative fiction's more cerebral authors, and I approached this young adult book with some trepidation. In that, I was partly right, and partly wrong.
Attanasio tones down both his vocabulary (some) and his customary ethereality to a level appropriate for intelligent youngsters. The story is fairly simple, though in some ways not credible. The protagonist, a 13 year old spelunker, thinks nothing of plunging immediately into a deep hole in the ground. Since she's otherwise moderately wise and rule-abiding, this seems unlikely. Unfortunately, that incredbility infects much of the rest of the plot. Many of the things that happen, and the choices the protagonist makes, just don't seem believable.
It's a shame, because the language is mostly smooth, the characters are likeable, and the general story is interesting. The reading level seems to vary sometimes between 8 and 15, but the mix is not really suitable for either.
All in all, a decent book, but not one you'd go back to. If you're looking for intelligent adult fiction, by all means, try Attanasio's other books. For the young adult in you, look further.