Some people really rave about it on golftuitiononline.com. The idea is that you learn three fundamental skills that get you to swing correctly relieving you of so many thoughts.
Here is how the method was explained in short:

Skill 1
hit down on the ball (Irons) to impart backspin and get a pure strike off the sweet spot of the iron. Drivers a parallel to the ground impact position.

Skill 2
Connect with the ball at the outermost point of the swing curve gives you a square contact

Skill 3
Turn the blade from slightly open to closed at impact for the boost in power

Skill one involves in part visualizing a nail going through the equator of the ball at a 20 degree angle to the ground as an impact and club angle reference. They also talked about putting a leaf on the ground in front of ball to which you hit down and through the ball.

Most people seem really excited about skill one. There seems to be more to it than I have explained here though. The guy who wrote the book is English and has a web site to purchase the book but some in the states were complaining about too much trouble to work out payment on the web site. The book is actually called Nail It!.