This is one of the best books on mastery that I've come across. It's much more than a bunch of summaries of studies and books on practice, it's the wisdom of some amazing teachers who spent a lot of time actually learning and teaching others how to master their fields. Most of the examples in the book are geared toward teaching teachers how to perform, however the techniques are easily applied to any field or endeavor.
The passion for learning the authors bring to the subject is palpable and the presentation is excellent. Also, don't be put off by the "42 Rules" in the title, this a rare exception to the rule that articles and books based on enumerated lists are no good.