Coraline - Neil Gaiman
Children scare much more easily than adults, but you're not allowed to give them too much gore, so writing a horror story that appeals to both is no mean feat. Neil Gaiman has written this for a fairly young audience, but it still managed to spook me in places - he's gone for creepy uneasiness and subtle nastiness rather than outright horror, and it works very well indeed. It's rather like a modern Alice Through The Looking Glass, which can't be a bad thing, and here the mirror world is much less benign.
The story starts out like any traditional ghostly yarn - Coraline and her parents move into a spooky old house (well, a converted flat in the spooky house, anyway) and, having nothing better to do, Coraline goes exploring. The neighbours are slightly strange, the garden is pretty boring, but there's also that door that doesn't go anywhere... Of course, the door eventually does go somewhere, and it goes to a darker but more interesting version of the real world. The stray cat can talk; the mad old neighbour's (imaginary?) pet mice have become a colony of singing rats, and a warped version of her mother with buttons for eyes doesn't want to let her leave. Coraline has to fight to save herself and all the others that have become trapped in this world.
The use of familiar places twisted into something nastier gives the book the unsettling feel of a nightmare. It's been a long time since wolves (or possibly crocodiles) have lived at the bottom of my stairs, but this taps into the memories of when those things were real. In the end, the simple style stops it being that scary for adults, as it's clearly a kids' book, but it's still pretty damn creepy in places. Coraline herself is a decently feisty heroine and there's no heavy-handed moralising; if I was a kid I'd have loved this, and I'm happy to recommend it to adults too.