A year or two ago I read Stephanie Grant's Map of Ireland, which I liked and admired, but don't remember all that strongly, and I didn't like and admire it enough to seek out other books by Ms. Grant. That was dumb because The Passion of Alice, her first novel is the perfect balance of cerebral and engaging. It's about a 25 year old in treatment for anorexia.
Alice's passion turns out to be a charismatic fellow patient--a bulimic. I assume we've all had people like this in our lives. They're exciting to be around, perhaps too much so at times, and they're often quite self-destructive.
Although Alice is an adult, the book should be appropriate for teens.