The story is about Coraline, a little girl who wants to live in a fantasy world, because she hates the world in which she lives. She is frustrated and upset with her mildly-neglectful parents who won't entertain her all day long, and she's an ungrateful whiner. She goes on to discover a real-life fantasy world, that gives her everything she wants, until she realizes that it's actually a curse.
Like all good little-girl heroines, she ends up slaying a witch, and her methods are not unlike those of Jael in the Old Testament book of Judges (by destroying her enemy through hospitality). She repents and learns gratitude, and in so doing, discovers that the real world is infinitely more magical then her escapist fantasies. In fact, in Coraline, Gaiman quotes directly from G.K. Chesterton and his chapter "The Ethics of Elfland" in Orthodoxy. This is where Chesterton explains the value of fairy tales because they open our eyes to the very every-day magic we are surrounded with (and ignore, because of our own dullness).
Just for two pre-warnings, the book is definitely creepy (and the illustrations more so), but by middle school age it would likely qualify as creepy and fun (not scary, as it may for some younger children). Also, there was a movie based on the book which came out several years ago. Do yourself a favor and avoid it completely. It changes the end of the book (no more Jael scene), and displays some pretty bad taste for something aimed at a G-rated audience.
