Cardigans for Every Body by Tian Connaughton
From Tian's website:
If you dream of crocheting and knitting your own sweater, Tian Connaughton, expert designer and technical editor, shares the secrets she's learned over the years. From her experience designing sweaters for popular mainstream publications and making garments for herself, she reveals the steps to achieving your perfect fit every time. Connaughton offers in-depth but approachable information on swatching, ease and fit, understanding schematics, how to use math to make calculations to modify existing patterns, and more.
In addition, Cardigans For Every Body includes four (4) cardigan patterns (2 crochets and 2 knits) and dozens of step-by-step calculations to help you develop a strong understanding of modifying any pattern to your perfect fit.