I finally picked this title up and boy am I glad.
The Appalachian Trail: Backcountry Shelters, Lean-Tos, and Huts by Sarah Jones Decker is more than just a book of great photos. It includes sectional maps of the Appalachian Trail and details on each of the lean-tos photographed. Each section also has a separate section on trail related information, including privies!
Here is a shot of the cover and you can buy it from the ATC.
The one thing I noticed is most of the lean-tos are fairly new so only a few are still standing from my hike in the 1970s.