Mathematical Needlework

 Mathematicians Sarah-Marie Belcastro and Carolyn Yackel collaborated on the perfect book for knitters who love mathematics and mathematicians who love knitting: Making Mathematics with Needlework: Ten Papers and Ten Projects. From the description: 

Every chapter (except for the introduction) has four sections. First, there's an overview intended for both crafters and mathematicians, so it should be understandable to mathematicians who don't know anything about crafting and also for crafters who don't know anything about mathematics. Then, there's a section of detailed mathematics which is intended for mathematicians. All of the authors have made an effort to include basic information so that mathematical enthusiasts who are not professional mathematicians can follow the bulk of the material. The third section of each chapter contains teaching ideas, and these range from elementary-school level to graduate level. Finally, every chapter has a project, with instructions written for and tested by crafters.

For more on mathematical knitting - and a few patterns - check out sarah-marie's mathematical knitting pages.