Jane's Historic Military Aircraft: Recognition Guide
There are a wealth of good and interesting books about the two World Wars: The Winged Watchman by Hilda Van Stockum, Enemy Brothers by Constance Savery, Flying Aces of World War I by Gene Gurney and many others. After reading a number of these, I began to wish for a book with pictures of the various types of airplanes in order to understand and appreciate the stories better.