I like the fact that you want contemporary materials for your research. Many of the books written during the thirties through sixties were probably overly romantic of the era; many of those written in the eighties or nineties were probably too caught up with the intent of tearing down and unglorifying war.
Most of the major aces' biographies were published, some during the war and some after. Those published during the war are often coloured by the times and must be viewed in the context that the conflict was still going on, and that the author had an understandably positive presentation of the facts (i.e. would not necessarily his reveal true emotions). Classics such as Winged Warfare by
Billy Bishop (ISBN 020-01024-075),
Flying Fury by
James McCudden (ISBN 441-24200-095) or The Red Baron by
Manfred von Richthofen (ISBN 441-71000-075)are contemporary (all but Bishop died before the war ended) but you have to read between the lines to get a truer understanding of what they went through.
I'd highly recommend No Parachute by
Arthur Gould Lee (09-002530-X, 1968). It combines letters written by him to his wife in 1917 with corresponding entries from his personal diary made at the same time. The contrast between the two sources is revealing. He was also just a regular flier, which is more indicative of the average pilot's experiences. Keep in mind that every pilot was an individual, however--generalizations are tricky.
Rudolph Stark's Wings of War (SBN 85368-389-1, 1933/1973) is good, and contains a beautiful account of himself and a British adversary breaking off a fight to the death to spend several minutes sharing a sunset flight together side by side, and then simply parting company.
Ernst Udet's Ace of the Iron Cross (ISBN 0-668-05163-9) shows considerable respect for his opponents.
Sagittarius Rising by
Cecil Lewis (67-12928) is an absolute classic autobiography and worth reading even if you don't use a word of it.
Although not contemporary,
The First of the Few by Denis Winter (ISBN 0-14-00-5256-9) is a first-class piece of research that you should read, and which will provide an excellent bibiography of additional materials.
Obviously these books have been published numerous times--the ISBN numbers I've listed are from my copies only.
Good luck and thanks for your interest in our subject!