Bennet, Alan. The Uncommon Reader. New York : Farrar, Straus and Giroux, 2007.
Bennet starts with a simple premise: "What would happen if the Queen suddenly developed an interested in reading for pleasure?" This short novel, a mere 120 pages, is a light exploration of that question, and shows how reading leads to neglecting one's duties and avoiding human companionship.
But it also shows how she grows through her reading. The Queen, after even just a brief exposure to fiction, seems to think more about the people around her, and show genuine concern for her staff in small ways that she never did before: reading, and exposure to the human condition, has given the Queen more of a heart, made her more compassionate.
(Sometimes it can be a stretch to fit a book into the theme, but I know I can do it!)