What is the best known novel by the author whose work was the basis for the French film Thomas the Impostor? 
Thomas the Impostor:  It is based on a novel of the same name by Jean Cocteau, which had first been published in French in 1923 and had been inspired by Cocteau's experiences in the first World War. Jean Cocteau:  Cocteau is best known for his novel "Les Enfants Terribles" (1929), and the films "The Blood of a Poet" (1930), "Les Parents Terribles" (1948), "Beauty and the Beast" (1946) and "Orpheus" (1949).
Les Enfants Terribles