This pearl of GM manuals should be found from every already practising or aspiring-to-be GM's collection. Yes, it's that great, even for folks who don't run Pathfinder. Well written, easy to understand, beautiful to look at... not to mention a well of inspiration it also achieves to be. It's a near perfect package of knowledge how to run smooth, richer, better RPG campaign. Sure, there are chunks of system specific stuff inside, but the most important bits of knowledge of how to run your game are universal and will fit in any system and game table. For juniors, it is essential. For the vets, well, if you're already good at what you're doing, you can always be better, and perhaps you're not perfect and can learn at least one useful new trick out of it.