Any book by Clancy is good. He is accurate in his military descriptions.
W.E.B. Griffin is good if he likes action. Don't get a book by his son, William E. Butterworth, Jr.
I think a winner would be a history of aviation book.
If he is really gung ho (that's an old Marine term meaning working together) about the Air Force, he might like something about the 8th Air Force during WWII.
