Well, first of all, he's my hero, and has been since I first attended one of his seminars back in 1987. More to the point, I'm far from alone in my appreciation of him, and here's why:
I described Edward Tufte as a graphic designer, but that’s not exactly right. His field is almost sui generis, containing bits and pieces of art direction, data-crunching, economics, historical research, and plain old expository writing. It’s often labeled “information architecture,” or “analytic design.” Tufte himself describes it many ways, but one is drawn from a classic piece of science writing: “escaping Flatland,” or using paper’s two dimensions to convey several more. Another, more acidic description: “getting design out of fashion and out of the hands of Microsoft.”
His four books have collectively been called a Strunk and White for design. Tufte works by showing both outstanding and horrid graphics he’s found, improving upon the latter, and his principles take on the meditative quality of Zen koans: To clarify, add detail. And: Clutter is a failure of design, not an attribute of information.