There is no required textbook or anything like that, but here are a few suggestions for books that are written in the spirit of a math circle.
- Mathematical Circles (Russian Experience), Dmitri Fomin, Sergey Genkin, Ilia Itenberg, American Mathematical Society, 1996.
- The Art and Craft of Problem Solving, Paul Zeitz, John Wiley & Sons, Inc., 1999.
- Problem Solving Through Problems, Loren C. Larson, Springer-Verlag, 1983.
- Problem-Solving Strategies, Arthur Engel, Springer-Verlag, 1991.
- Kvant Selecta: Algebra and Analysis, I and II, Serge Tabachnikov, (ed.), American Mathematical Society, 1999.
- Problem Solving Book with contests and solutions from around the world 1999-2000.