The Postmarks of Aden: Postal Markings 1839-1939 by M. H. Robertshaw
Along with A. L. Hine-Haycock, Robertshaw was the pioneer investigator into the stamps and postal history of Aden. Published in 1946, this is the updated and standard reference book on the subject covering the various post offices of Aden including Aden Steamer Point, Aden Cantonment, Aden Camp, etc.
The rare hardbound version in grey cloth with thicker papers than the softbound version. In very good condition save for some toning on the front and back endpapers and a presentation marking on the front endpaper.