This is the best advanced-level book on GMing that I have ever read. While other books cover the fundamentals and help you orient to the principles of running games, this book forces you to look at how you prep, how you run, and how you think about your game. It's written from an old-school perspective by a master of the old-school game, but the advice is useful for almost any game type. It's written in a highly entertaining, blog-style that holds your interest from start to finish. I have read this book cover-to-cover at least three times since purchasing, and I would recommend it to anyone who wants to transition from intermediate- to fucking boss-level game mastering.