Speak, by Laurie Halse Anderson

This was a difficult book to read;  well-written, but painful.  Melinda enters high school as an outcast, with the memories of something terrible shutting her in her own mind, unable or unwilling to say more words than are necessary. 

This is an "issues" book, but it isn't flat.  I wouldn't be likely to recommend it to teen readers simply looking for something entertaining, but it's perfect for high school study.  I expect it's helped a lot of young folks either find their voice or understand someone else's over the years.