My own favourite is Flight Into Hell by Edwin C Parsons. Disregard the pulp-fiction sounding title, this is a well written account of his time in the original Lafayette Flying Corps. Parsons chose to stay with the French Air Service instead of transferring to th Americans and later flew with Spa 3. Les Cigognes. My copy is dated 1938, a lucky find on a backstreet bookstall.
On line you should be able to find these:
The Lafayette Flying Corps by Hall & Nordhoff (2 vol).
Go Get ‘Em by William Wellman.
Journal des marches et op?rations pendant la campagneby Georges Thenault (2 vols). Handwritten mission logs.
One man’s war : the story of the Lafayette escadrille / by Lieutenant Bert Hall and Lieutenant John J. Niles.
High Adventure A Narrative of Air Fighting in France by James Norman Hall.
Flying for France. With the American Escadrille at Verdun by James R. McConnell (James Rogers).