Following up on several threads I went to Barnes & Noble to check out some of these books:
Aces High
Under the Guns of the Red Baron
German Knights of the Air
Air War 1914-1919: A Pictoral History
All were on the bargain rack for less than $20 USD.
I particulary found the Red Baron and the German Knights books the most interesting as they were both basically historical biographies.
Under the Guns of the Red Baron is a victim by victim account (biography) of each of MvR's victories. While German Knights was an Ace by Ace biography of each 'Pour le Merite' bearer of Germany. Not to dissimilar from the WWII book 'Horrido' (also very good).
If anyone can locate a copy of "The Fighters" by Thomas Funderbunk, I believe you will find it quite good. I bought mine about 20 years ago. I kick myself now but back then I sold, "The New York Times Book of WWI" @ a garage sale for $1.