While the rest of the family moved to the ground floor, Michel camped out with soldiers in the attic. “I will never forget the smell of the Wehrmacht, the compound of tobacco and boot polish,” he wrote. “For me this was the fragrance of happiness.”

His school performance improved, and he enrolled in the Sorbonne, where, entranced by the philosopher Gaston Bachelard, he took a degree in philosophy and law. Four years of German philosophy at the University of Tübingen followed. But when he returned to France in 1949, he failed the philosophy exam that would have certified him as a university teacher.

With an academic career beyond reach, he began producing radio and television programs and writing literary journalism. He was, for a time, the press agent for a new radio station, Europe 1. He was fired after four years but landed on his feet, becoming the literary director of Editions Plon, a large publishing house.

In the meantime, he began working on the novel that would become “Ogre,” his attempt to deal with Germany and World War II in fictional terms. Fascinated by the idea of the Nazi regime as a devourer of children, especially in the Hitler Youth, he created an ambiguous French protagonist who combined the attributes of the medieval child murderer Gilles de Rais, Goethe’s predatory Erl King and, paradoxically, St. Christopher, who according to legend transported the infant Jesus across a swollen river.

The scope and the complexity of the novel caused him to put it on the shelf while he completed “Friday.” “It took me 15 years to reconcile fiction and philosophy using myths as a vehicle,” he told the reference work World Authors.

The novelist Raymond Queneau read “Friday” in manuscript at the prestigious firm Gallimard and urged it on his fellow editors. The firm’s investment earned dividends when Mr. Tournier went on to collect prizes and, in 1972, join the jury of the Prix Goncourt. He returned to “Friday” and produced a simpler version, published in English in 1973 as “Friday and Robinson: Life on Speranza Island.” Marketed to young readers, it sold in the millions.