This is quite a short book, a quick one-sitting read for an adult, but really more of a YA book although with "mature" themes so I'd say teenagers rather than tweens (nothing too racy, but there are dismembered bodies, and vibrator/masturbation jokes).

It's about a boarding school for oddball children - not an unusual premise for a YA book - but in this particular case, the children are those who had been "lost" in various fairylands/alternate worlds, and have now returned to this one and cannot readjust. These are the children who went Through the Looking Glass to Wonderland, or through the wardrobe to Narnia, and so on, and then came back, having lived years in those other worlds, often to find themselves back in young bodies they no longer feel attached to, and with parents who still expect a different person than the one they are now. So the parents take them to board at this school, and the lady who runs the school tries to help them readjust, and come to terms with their loss (because it's a loss to all of the kids who come here - they all want to go back, and for various reasons, cannot get back).

It's an interesting premise which isn't too unusual on the face of it, but McGuire creates a framework of structure by defining the different types of world (Nonsense worlds and Logic worlds and Wicked worlds and Virtue worlds and variants of each), and also by postulating that the doors appear to the children in the first place to take them into these worlds because of some element that the child needs. A deeply suppressed, quiet child goes to a nonsense world where she can discover and finally express her exuberance for life. An unhappy girl goes to a Logic world where she discovers she is really a he inside - and then is sent to the school by parents who cannot accept this. And so on. It's not really a great leap but codified neatly into a system of alternate worlds that's tied together through this school for wayward children.

And when students start turning up dead shortly after the newest girl Nancy arrives at the school, not only are all the students' lives in danger but so is the future of the school, if word gets out and parents force the school to shut down.

I liked this a good deal more than McGuire's badass-snarky-urban-heroine-in-high-heels books and might consider picking up some of the sequels.