I interview William Cook, math professor and author of "In Pursuit of the Traveling Salesman Problem: Mathematics at the Limits of Computation" about his new book, and about how he got sucked into tackling a famous unsolved problem. We discuss why the problem is so intriguing, how young people can explore it, interesting applications, connections to other famous problems, the iPhone app that solves large instances, why the military cares about the problem, and more.