I Can't Tell You, by Hillary Frank

This book takes place all in written communication: the main character, Jake, has decided to stop speaking since talking has gotten him into "so much" trouble. In the process of note-writing, Jake finds out that more important than talking, it is critical to tell the truth about what's going on in his head, and how to do it appropriately, i.e. not when you're angry and just shouting out facts.

Fun book to read. I've just remembered why I like "young adult" novels.