Simone de Beauvoir’s lost novella of friendship

Inseparable. By Simone de Beauvoir. Translated by Sandra Smith. Ecco; 176 pages; $26.99. Published in Britain as “The Inseparables”. Translated by Lauren Elkin. Vintage Classics; £12.99

IN 1958, IN “Memoirs of a Dutiful Daughter”, Simone de Beauvoir recalled meeting Elisabeth Lacoin in 1917, when she was nine. On the first day of the school year, de Beauvoir found that “the seat next to mine was occupied by a new girl: she was small, dark, thin-faced, with short hair.” Lacoin explained that she had been confined to her bed for a year after her dress caught fire and she suffered terrible burns. De Beauvoir was captivated by the story, and by her. “Nothing as important as that had ever happened to me,” she later wrote. Lacoin “seemed to me a very finished person…everything she had to say was either interesting or amusing.”

The pair quickly became firm friends—dubbed “the two inseparables” by their teachers—as well as academic rivals. They would sneak into Lacoin’s father’s study, not to exchange “girlish confidences” but to talk about their reading and schoolwork, or lofty ideas such as the definition of love. They remained close until university.

Though de Beauvoir’s family had once belonged to the haute bourgeoisie, her father had mismanaged...