Just finished a really interesting book called, Quiet: The Power of Introverts in a World That Can't Stop Talking written by Susan Cain. The author herself is an introvert and provides insights and validation to the benefits of being "quiet."
I get a lot of questions from introverts on how to mingle and make friends, and while quiet doesn't speak to those type of relationships, it does offer a lot of information about how introverts succeed. This can be extremely helpful when developing relationships. Many times introverts are brought up to try and change in order to "fit in" with their extraverted family members or friends, when really they don't need to change, they just need to figure out how to be understood. Quiet can help do that. Here's more about my review of the book.