Essays on the Sociology of Perception by Mary Douglas
First published in 1982, this is one of Mary Douglas' favourite books. It is based on her meetings with friends in which they attempt to apply the grip/group analysis from Natural Symbols. The essays have been important texts for preparing grid/group exercises ever since. She is still trying to improve the argument of Natural Symbols and is always hoping to find better applications to illustrate the power of the two dimensions used for accurate comparison.