I've been running RPG games since I got the red box set at age nine. I'm damn good at it. Better than most I've met.
That being said, I bow before the genius of this book.
Return of the Lazy Dungeon Master breaks the creation of a gaming session into simple steps that can be completed within an hour or two. What's more, the vast majority of games will actually be improved using these methods. In his book, Mike Shea has focused in on what makes a RPG adventure great with an intensity that would put a beholder's eye-beams to shame.
I've read a lot of how-to-DM guides, from the latest DMGs for Pathfinder and 5e to Gygax's old Master of the Game and too many Dragon Magazine articles to recall. This book tops them, and makes it look easy.
The only downside to this book is that it isn't for brand-new DMs. If you've never run a game before, don't start here, it assumes knowledge you don't have yet. Once you've been at it for a year or so, however, come pick it up. Return of the Lazy Dungeon Master is an absolute must-have, and a steal at the list price.