The books that help you most are those which make you think that most. The hardest way of learning is that of easy reading but a great book that comes from a great thinker is a ship of thought deep freighted with truth and beauty.
Charles was very intent to use his years as Prince of Wales to make his mark while he still had freedom of maneuver that he wouldn't have as King. The first subject he really went for was architecture. It made an impact.