Minor White (1908–1976)

The concepts are great and still relevant today. Few use film these days, and even less use a darkroom. However if you want a big print of an old B&W negative there are some useful technical tips here.
My high rating is due to the important influence this book and concept had.

Ansel Adams passed on the teaching of his system of Black and White film exposure and development to Minor White, who joined with experienced teachers Zakia and Lorenz to write this definitive explanation and manual for understanding and using the Zone System.