Fiction by Ned Vizzini.
This is a story about teenage boy in Manhattan who has a loving family and gets good grades at a challenging high school. Unfortunately he also wants to kill himself.
Obviously this kid goes to a mental hospital. That's what the story is about.
The author does a good job of really helping you see this character from the inside. I actually believed that this dude with the near-perfect life was in abject despair. It's a very interesting character study.