"The 120 Days of Sodom and Other Writings by Marquis de Sade" is a collection of writings by Marquis de Sade along with two essays about his work that examine his philosophy and importance in literature. Each section is provided with introductory information by the editor.

The collection opens with an essay by Simone de Beavoir that asks, "Must We Burn Sade?" which seeks to examine Sade's legacy and form a picture of his ethos based on apathy and atheism. This is followed by an essay by Pierre Klossowski who discusses Sade's notion of God and Nature as destructive forces and who disagrees with Simone de Beauvoir on some major points regarding Sade's atheism.

The second part includes two pieces by Sade from his collection entitled "Les Crimes de l'Amour," "Reflections on the Novel." and "Florville and Courval." "Reflections on the Novel" lays out Sade's idiosyncratic history of the novel, tracing its roots back to the Egyptians. He provides his assessment of several contemporary writers and their works, and then gives his own advice for writing good novels. "Florville and Courval" tells the complicated story of a woman who unknowingly and through no fault of her own, finds that she is married to her own father, has been raped by her son who she has had with her own brother, and has sent her own mother to the gallows. A contemporary review of the collection by a journalist named Villeterque is included in which this and other stories are soundly condemned. Sade's scathing response to Villeterque is also included.

Part Three of the collection is made up of Sade's most well-known work, "The 120 Days of Sodom." This fragmentary novel, composed while Sade was imprisoned in the Bastille in Paris, was believed to be lost by him but was later rediscovered. Its publication was suppressed until the 1930s. It tells the story of four wealthy friends who arrange a four-month long orgy of sexual and criminal indulgence. The novel is essentially an extended fantasy of hundreds of different depraved activities that ends in the deaths of many involved.

Part Four includes two more pieces by Sade, the play "Oxtiern," and the short story on which it is based, "Ernestine." These two pieces, which have dramatically different endings, form an interesting comparison. They tell the story of a woman named Ernestine who is raped by the Count Oxtiern, who has removed her fiance from the picture by having him framed for theft. Ernestine plots her revenge on the Count, who despite his own evil schemes is finally brought to justice. The form of justice given out is different in each version however.