This collection consists of over 400 letters from writer, philosopher, and feminist theorist Simone de Beauvoir (1908-1986) to her mother, Françoise de Beauvoir (1887-1963), and sister, Hélène de Beauvoir (1910-2001), who was also known as Henriette, dating from October 1918 to December 1968. These letters contain extensive documentation of Beauvoir's personal life, travels, writings, and intellectual process. Roughly fifty of the letters were written from when Beauvoir was 10 to 19 years old and provide important documentation of her childhood and youth.

In total, there are 440 handwritten letters, 38 postcards, and two telegrams, as well as several handwriting practice sheets from Beauvoir's childhood. Correspondence sent to Beauvoir's mother comprises 315 letters (from one to ten pages in length), as well as postcards and telegrams, dated from October 1918 to September 20, 1957, many of which were sent during her travels and are often written on letterhead from breweries, restaurants, or hotels. These letters are rarely precisely dated, though several have been dated later by Françoise or Hélène. Some are also signed by Hélène, often under the pet name "Poupette." Correspondence sent to Beauvoir's sister, who was a painter, comprises 92 letters dated from November 1924 to December 1968 (mostly 1949-1966). Most of these letters are dated with red ink by Hélène, who added the name of places she stayed when she received them. Letters to Beauvoir's mother span from her childhood and early adulthood, her relationship with Elisabeth "Zaza" Lacoin, her teaching job in Marseille, life in Paris and participation in the French Resistance during WWII, through the peak of her writing career. She describes her life in much detail, including about trips, what she was reading, her relationships, and her progress in her writings. Over time, she begins to write more openly about her non-monogamous extended family structure (which she called her "petite famille") that included Jean-Paul Sartre, Jacques-Laurent Bost, Olga Kosakiewicz, Bianca Bienenfeld, Natalie Sorokin, Michel and Louise Leiris, Raymond Aron, Alberto Giacometti, and others. Beauvoir's letters to her sister also discuss her friends and lovers, including Nelson Algren and Claude Lanzmann, as well as her travels, reading, and writing, but are more spontaneous in nature and provide additional anecdotes on her books such as Les Mandarins and Le Deuxième Sexe. The letters overall provide significant insights into Beauvoir's most famous published works, as well as her personal and professional life.