It introduces a specific method to write concise, effective business documents. Then it shows how you can use the method to critique your own thinking.
Finally, one late night, sitting across from my managing director (the leader of a prestigious boutique pharma-consulting firm), I asked him rather bluntly, "How did you learn to speak so well?" He gave me a rather blank stare, and thought for a little while. "Ah!" he exclaimed, jumping up from his desk and darting over to his bookcase. After a little rummaging, lo and behold, he pulled out an old copy of the Pyramid Principle. I leafed through the book and found a number of notes and highlights as he explained to me that what I held was the single most influential book he'd ever read. He told me to read it, not as a way to structure presentations or emails (although it helps there), but as a new lifestyle. Fold the ideas and principles into your very being, so as to become second nature, and you'll never have trouble communicating again.
It's a must-read book.
The author approaches communication from the principle of Gestalt psychology and really helps one understand how our minds communicate.