Oaxaca al gusto, an infinite gastronomy (2010)

Diana Kennedy's late book on a single state, published by the University of Texas Press in 2010, won the James Beard Foundation's Cookbook of the Year award the following year. It is a serious book for serious cooks, with ingredients you may have to hunt for and a level of detail that rewards patience. Kennedy treats Oaxaca as a cuisine in its own right rather than a single famous mole, which is exactly the lesson this list is about. Buy it once you are comfortable with the basics.