Ansel Adams, The Camera   (**) From the basics of light and how it is captured, a valuable reference on taking photographs.

Ansel Adams, The Negative   (***) The much used and abused Zone system revealed in depth.  Understanding the basic principles of exposing for the right shadows and then developing for contrast is of tremendous value, whether or not you do your own development.  The same principles apply today, no matter how sophisticated your equipment, or whether you are doing digital image editing or relying on your trusty enlarger. Whether or not you come to believe in the zone system or use it, this was one of the first popular works to explain how to manipulate contrast throughout the imaging process.

Ansel Adams, The Print   (**) From detailed instructions on how to print black and white negatives to practical advice on mounting and displaying your work there is something here for everyone.

Ansel Adams, The Making of 40 Photographs.  (***)  Adams takes you through the details of creating 40 of his favorite and most famous images.  Not as packed with advice as some of his other works, but well worth reading to learn about how he came to make these photos and what he has learned over the years.