In a recent issue of Science, Gary Urton reviews a new book with the above title. The authors are Marcia and Robert Ascher, who have studied roughly 200 Inca quipus, demonstrating in the process that the Incas did indeed have a "written" language as well as a surprisingly sophisticated system of mathematical notation. A quipu appears to the uninitiated as a meaningless jumble of strings. To an Inca quipu reader, though, the positioning and colors of the secondary and tertiary strings appended to the primary cord all have meaning. The knots along each string also convey messages. Quipus incorporated, in a sense, three-dimensional notation, as opposed to the two-dimensional text on this page. Inca mathematical developments are inherent in quipu notation, which clearly reveals base-of10 positional notation and the use of the zero. Instead of a tangle of colored strings, the quipus actually display sophisticated concepts of number, geometrical configuration, and logic.