I've read quite a few coming-of-age novels, and this one starts off in pretty much the same way. Lonely teenager is stressed and nothing seems to be going right. The difference here, and it's a fairly big one, is that the main character is suffering from depression.
The depiction of an adult psychiatric hospital isn't very realistic, but it didn't matter to me. There's an authenticity to the book that made its flaws seem much less important. It's funny, maybe a little sappy, but it's also warm and honest. It's a little too happy for the subject matter, but the characters and their feelings seem real.
RIP Ned Vizzini.