In his classic *Knot Book*, Colin Adams relays the story of a hapless undergraduate who inquires of his calculus professor, “What kind of math do you study”. When the professor replies, “Knot Theory,” the student responds, “Oh good! I don’t like theory either!” The misunderstanding aside, the student’s response points to one of the delights of knot theory: one can learn and understand a fair amount of this subject without needing a lot of mathematical knowledge or technique. Indeed, knot theory might be the perfect way of enticing a mathematically bored middle or high school student into deeper and more interesting waters.

*Knots Unravelled* is a wonderful gift for such a student. It is slim, easy to read, and filled with delightful mathematical ideas. After beginning with a history of knots and knot theory, each chapter addresses some aspect of the mathematical theory of knots. The topics range from knot diagrams and the Reidemeister moves, to crossing number, unknotting number, 3-colorability, and the Jones polynomial. Only the last chapter, on the Jones polynomial, assumes any high-school algebra. Between the chapters are interludes which explore specific examples of knots. These include the Celtic knots and the more prosaic but tractable torus knots.

The organization and writing of the book are superb. I read it in an hour on a plane flight. The discussion is appropriately informal and is interspersed with exercises called “tasks.” Many of the tasks are straightforward but non-trivial. A dedicated high school student could enjoyably pass quite a bit of time drawing pictures or playing with string in an effort to solve them. Solutions to the tasks are in the back, so even if the student is not dedicated, they can still learn how to solve the problems.

For readers who want more mathematical rigor and depth, the aforementioned book by Adams is a great place to start. From there, the reader can progress to any number of other undergraduate and graduate texts.

**Reference:**

Colin Adams, *The Knot Book*, American Mathematical Society, 2004

Scott Taylor is a knot theorist at Colby College who is just occasionally “not a theorist.”