Consists of nearly 300 letters from Simone de Beauvoir to Violette Leduc documenting their literary friendship spanning four decades, along with 23 notebooks containing manuscript drafts of Leduc's autobiography, La Bâtarde (1964), which recounts her life from birth until the end of World War II. Beauvoir was a literary mentor to Leduc since their meeting in 1945, and she encouraged Leduc's writing by serving as a first reader and editor, helping her find a publisher, and assisting her both artistically and financially throughout her life. Beauvoir also wrote the preface for La Bâtarde, and two of Leduc's notebooks in this collection are inscribed to her. The notebooks contain over 2,000 pages of writing composed between 1958 and 1964, which include corrections, added paragraphs, erasures, and unpublished passages, and document the evolution of the text over time.

The letters span Beauvoir and Leduc's entire friendship from their meeting in 1945 until Leduc's death in 1972. In an early 1945 letter, Beauvoir gently but firmly states that she does not reciprocate Leduc's romantic feelings towards her, and establishes their relationship as a friendship and literary mentorship. Beauvoir writes from various places in her travels, including the United States, Cuba, England, Italy, Greece, the USSR, and Norway, which she visited with partners Jean-Paul Sartre and Claude Lanzmann. Beauvoir discusses in detail her own readings, travels, and the progress of her work as well as the literary, artistic, and political life of the time. Her letters also provide deep insight into her mentorship role with Leduc, guiding her and urging her to write, providing feedback on Leduc's drafts, and regularly reassuring her of their friendship. The letters also discuss how Beauvoir and Jean-Paul Sartre arranged for Leduc to receive a regular allowance from the publisher Éditions Gallimard, and Beauvoir's outrage over Gallimard's censorship of the first section of Ravages (1955), which recounted Leduc's lesbian relationship with a fellow classmate, Isabelle P. and was later published as Thérèse et Isabelle in 1966. Letters from the late 1950s and early 1960s discuss Leduc's progress and Beauvoir's editorial work on La Bâtarde, and following the book's publication in 1964, Leduc's popular success and media attention due to her work's erotic and culturally taboo content. Subsequent letters discuss later books and writing assignments. The letters also allude to Leduc's struggles with her mental health and stays in various psychiatric clinics, and her deteriorating health beginning with her breast cancer diagnosis in 1965 until her death in 1972.