I read his book, first I was disappointed, because he would show me, how to draw simple pictures, that I could use in my own presentations, but then I understood what he was really going to explain in his book: He shows us that we should differentiate between “See”, “Look”, “Imagine” and “Show”, when we talk about Visual Thinking. He explain, what he means on his website, too.
What his book did for me, it showed me how my process of recognizing the world works. And this will help me to explain my ideas in future better. I know it, because I tried it. I works. The Back of a Napkin, by Dan Roam