Black Thursday by Martin Caidin (Dutton, 1960). Recounts a bombing raid that has been called "the worst single day in the history of the Eighth Air Force." The mission: to destroy ball-bearing factories in the German city of Schweinfurt. The result: 60 U.S. bombers lost, more than 600 crewmen dead, and the factories damaged but still standing.
The Narrow Margin: The Battle of Britain and the Rise of Airpower 1930-40 by Derek Wood and Derek Dempster (McGraw-Hill, 1961). An excellent account of the legendary battle.
Wings of Morning by Thomas Childers (Perseus, 2000). The author's uncle was killed when the very last U.S. bomber to be shot down over Europe, a B-24, crashed. Childers found out how, and why.
Flying Tigers by Daniel Ford (Smithsonian Institution Press, 1991). Working with Japanese, British, and American archival records, Ford, an Air & Space contributor, pieces together for the first time what may be the most accurate accounting of the combat victories and losses attributed to the American Volunteer Group, or Flying Tigers, during the two years they fought Japanese forces in China and Burma.
Low Level Mission by Leon Wolff (Berkley, 1958). The story behind the enormously costly and ultimately unsuccessful campaign to put the refineries in Ploesti, Romania, out of commission.
Allied Aircraft Piston Engines of World War II by Graham White (Society of Automotive Engineers, 1995). White's encyclopedic treatment covers every manufacturer in the United States and Great Britain, every engine they made, and the aircraft in which the engines were used. Advances in engineering and technology that supported the Allied war effort spanned everything from fuels to metallurgy, and it's all covered here.
Flying Fortress: The Illustrated Biography of the B-17s and the Men Who Flew Them by Edward Jablonski (Doubleday, 1965). An overall look at the beast, with copious black-and-white illustrations.
Falling Through Space (Wings of War) by Richard Hillary (Reynal & Hitchcock, 1942; Time-Life Books, 1991). Only half of the book is about flying a Spitfire in combat. The rest recounts what it's like to recover from the horror of being nearly incinerated in one.
The First and the Last: The Rise and Fall of the Luftwaffe, 1939-1945 by Adolf Galland (Holt, 1954; Buccaneer Books, 1997). A history of the war from the perspective of a leading Luftwaffe ace and general. (The book includes a few of the author's less proud moments, such as the time his airplane collided with a lamppost.)