It's Kind of a Funny Story by Ned Vizzini

I picked this one up because the movie looks good (Zach Galifianakisi as a mental patient? OK!), but I like to read the book first, if possible, before I see the movie.

Craig's not just a darkly mooded teenager - it's much worse than that inside his head. Taking the one good piece of advice he gets from the worst suicide hotline operator ever, Craig walks down the street to the hospital and checks himself in. The people he meets and the things he learns on the ward will force a true shift in Craig's head and in his life.

It's a good book; funny, and yet heartwarming. While the book's resolution is perhaps a bit too glossy and pat, much of the book rings true and many readers will find bits of themselves inside Craig's head, too.