The Outliers by Malcolm Gladwell

This is regarded as the main text that brings the now well known concept of 10,000 hours need to be spent via deliberate practice to become a world-class expert at a skill.  Skills are wide ranging such as computer programming or playing the violin.  Mentions interesting case studies backing this from Bill Gates to the Beatles.  So there you have it, three hours per day is what you need to put in for ten years dedicated to one skill is what you need to do to become an expert.