I think that Eric Alan's Wild Grace: Nature As a Spiritual Path is also a wonderful book; it has a lot of great spiritual writing, but the photographs (all from color negatives) are also just outstanding-- in my opinion. My style tends to lean towards the more quiet and contemplative style and if you appreciate that kind of photography (I think most do) then you'll like his photographs.
By far though, one book outweighs any other, and that's Recording Historic Structures. Most of the photographs are just typical HABS/HAER (i.e. mostly standard architectural and industrial shots) but there is one photograph in the text that I think needs to be on every photographer's wall.
Anyway, one photograph is of one of the HAER photographers, Eric DeLony, who is standing on a water pipe doing field shots with a TLR, and the pipe he's standing on looks like it's at least forty feet above the water. I've always loved the photograph of St. Adams standing on his car with his camera set up, but I think that this portrait of Eric DeLony beats any photographer's portrait that I've ever seen. I actually cut out the photograph and put it on my wall, I love it that much!
The only unfortunate part about the portrait is I really want to get a portrait of me in a similar situation, balancing on a pipe or trunk above some sort of certain doom, just calmly looking into my waist level finder...