The square root of 2 is a fascinating number - if a little less famous than such mathematical stars as pi, the number e, the golden ratio, or the square root of -1. (Each of these has been honored by at least one recent book.) Here, in an imaginary dialogue between teacher and student, readers will learn why v2 is an important number in its own right, and how, in puzzling out its special qualities, mathematicians gained insights into the illusive nature of irrational numbers. Using no more than basic high school algebra and geometry, David Flannery manages to convey not just why v2 is...