In interwar Poland, Rokhl Auerbach (1899-1976) made a name for herself in Jewish literary circles and befriended modernist writers like Bruno Schulz, whose career she helped launch. When the country was plunged into war in September1939, her friend and mentor Emanuel Ringelblum, a historian, persuaded her to stay in the Polish capital and run a soup kitchen. “Not everybody is allowed to run,” he told her.

Auerbach started cooking, she writes, on “the very day that Hitler came to Warsaw to review the victory parade.” Her kitchen, enclosed within the area sealed off into a ghetto in November 1940, was soon serving some 2,000 malnourished “customers” a day with thin soup made from hard barley and oat pellets, sometimes supplemented by a slice of black bread “adulterated with clay and glue.”

Auerbach’s position on “the front lines of the battle against hunger,” as she puts it, afforded her a unique view of a “historical cataclysm that played itself out in an infinite number of individual variations.” Like the Warsaw ghetto diarist Chaim A. Kaplan, she describes streets teeming with peddlers, smugglers and singing beggars. She is especially acute when she shows ordinary people trying to keep their dignity and decency in such circumstances.

The ghetto’s ethos of solidarity and self-help, Auerbach observes, depended on cultural nourishment no less than the caloric kind. Leszno Street, for instance, was home not just to Auerbach’s kitchen but also to theaters—locals referred to it as the Broadway of the ghetto. Auerbach presents figures who embodied what she calls “an affirmation of life in the face of death”: librarians who lent books to children, lecturers who held audiences in rapt attention, former members of the Warsaw Philharmonic who performed Mozart piano concertos, and a poet, Shlomo Gilbert, who A storied memoir and searing document from the Warsaw ghetto, now translated into English. After soup had been served “would pull some papers from his pocket and start to read anew scene from his long dramatic poem about arguments between the people and God.”

Words fail her only when Auerbach witnesses the roundups conducted by “emissaries of the angel of death,” as she calls the Gestapo, and the mass deportations from the ghetto—beginning in the summer of 1942—to the deathcamp at Treblinka. “We need a new Goya,” she writes, to describe such a “deluge of destruction.”

As the Nazis surged against the ghetto’s half-million Jews, Auerbach sometimes bent her own rule of keeping all food portions strictly equal. She gave extra food to a survivor of Dachau, who had ended up in Warsaw after being freed from the German concentration camp outside Munich. “I would regard it as the greatest defeat for our kitchen if we can’t keep a person like this alive,” she writes. When he succumbed to hunger anyway, Auerbach despairs. “I had better luck saving documents than saving people.”

The documents Auerbach is referring to were at the heart of a clandestine project that Ringelblum was leading under the cover of relief work. A secret archive—the subject of a previous book by Mr. Kassow—preserved firsthand reports, demographic studies, pages culled from some 50 underground newspapers, placards and posters, diaries and letters, photographs and drawings. In1999, UNESCO entered three collections from Poland into its Memory of the World Register: Copernicus’ scientific manuscripts, Chopin’s musical scores and the Warsaw ghetto archives.

At enormous personal risk, Auerbach helped Ringelblum assemble this mosaic of memory and contributed to it her own writings, including her raw 1942 interview with a new escapee from Treblinka. To retrieve as much as possible of the irretrievable, Auerbach writes, became “the sole reason for my survival” and the source of her resilience. “As long as I keep ongoing,” she adds, “though lost in a vast void, engulfed in a fog of unwept tears, I will remember, and I will record.”

When she escaped the ghetto in March1943 by assuming a Polish identity, Auerbach carried that sense of determination to the “Aryan” side of the city, where she remained for the rest of the war. Using forged papers, perfect Polish and fluency in German (“which I would like to forget forever,” she remarks), she served as a courier for the Jewish underground and filled seven notebooks with her observations of the ghetto.

A year after Auerbach’s escape, the Gestapo captured Ringelblum from the bunker where he had been hiding, took him to a prison in the now razed ghetto, and shot him, his wife and 12-year-old son. Of his 60 colleagues who took part in assembling the archive, only Auerbach and two others survived. After the war, Auerbach was instrumental in unearthing a cache of the archives, which had been buried in 10 tin boxes, from the rubble of Warsaw’s necropolis. “I, by myself, agonized and suffered to bring them once again into the light of day,” she writes. When Auerbach left Communist Poland for Israel in 1950, she reports, “I never parted with them, either on the train or on the boat.”

Nor could she part from the imperative to “give voice to our sorrow and our fury.” In the mid-1950s, Auerbach created the witness-testimony department at the newly founded Yad Vashem, Israel’s Holocaust memorial. Her pioneering approach was vindicated at the 1961 trial of Adolf Eichmann, an architect of the “Final Solution.” She fought vigorously for the prosecution to rest not only on official wartime documents, most written by the perpetrators, but on survivor testimonies. “Ringelblum was the first to start with the writing of a great indictment,” she testified at the trial in Jerusalem, “and there is a direct path leading from that place to this courtroom.”

In “Yizkor, 1943,”an elegy for the ghetto, Auerbach writes: “And if, for even one of the days of my life, I should forget how I saw you then, my people, desperate and confused, delivered over to extinction, may all knowledge of me be forgotten.” Thanks to her indispensable chronicle, and to Mr. Kassow’s deft translation, there is no danger of that.

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