The GameMastery Guide is a wonderful tool for those who wish to truly master the difficult task of being a competent GM. The guide may, at times, seem redundant or basic to advanced GMs, but by expressing the simplest game-mastering concepts, the guide helps to establish the essential nature of the fundamentals of any RPG as well as emphasizing their importance in the hearts and minds of all talented GMs. Can someone be a GM without The GameMastery Guide? Yes. Will that person be a better GM if they own and use this guide? Absolutely.
Also... the world building section is pure creative genius, not just for GM, but writers as well.
