I have a good one for you. It's by Laurie Halse Anderson and it is called "Speak." The whole book is written in diary format by a girl named Melinda who basically loses the ability to talk to others around her after a traumatic incident. I cannot explain more about what the trauma is about without spoiling some elements, so you'll just have to take my word for it that this is a really good book. I found out much later that the author actually based some elements of the story on her own life, which is a bit sad, but explains why she was able to write everything in such a clear and expressive manner.