By far, this is the best comprehensive account I've yet come across of the development of American air power (U.S. Army) during the First World War. Besides providing a full and detailed history of the development and deployment of fighter, bomber, observation/reconnaissance, and balloon units on the Western Front, the author also shed light on the training and combat service of American pilots with Italian air force units on the Italian front and over the Mediterranean and Adriatic Seas against the Austro-Hungarian Empire.
Furthermore, this book is all the more remarkable because the author was able to personally contact many of the surviving veterans (who, in the 1960s, were still plentiful). Any aficionado of First World War aviation should have this book in his/her library.