Most of us know Stein far better for her prescient patronage of modern art than for her dense- ly inhospitable modern prose. With her brother Leo, she began to collect C?zanne, Picasso and Matisse when the artists were nobodies. She filled her flat at 27 rue de Fleurus with paintings, and opened the doors to the demimonde of Paris. Toklas entered the picture just after Picasso painted his portrait of Stein, now in the Metropolitan Museum of Art, in 1906. When Toklas saw the painting, she complimented Picasso: “Yes,” he said, “everybody says that she does not look like it but that does not make any difference, she will.”

That anecdote comes from Stein’s one popular book, “The Autobiography of Alice B. Toklas,” which Stein wrote in Toklas’s voice. Published in 1933, the witty memoir jump-started a wider interest in the two ladies’ lives, helped along much later by such accounts as Hemingway’s “A Moveable Feast.” But the book that hooked Malcolm was “The Alice B. Toklas Cookbook,” which came out in 1954 and had a snobby appeal for those who looked down on Eisenhower’s America. Tucked among such haute cuisine recipes as “Cock in Wine” were Toklas’s own memories of life with Stein. (The book had a second success in the 1960s, thanks to the inclusion—cut from the first U.S. edition—of a recipe for hashish fudge.) What intrigued Malcolm was the chapter on cooking during the Nazi occupation of France—not the recipes based on rations, but the underlying question: how did two American Jewish lesbians survive the Nazis while living openly in their French country house?

Stein and Toklas were warned to leave France but never did. They had a protector: a French scholar and longtime friend of Stein’s named Bernard Fa?. Fa? was closely connected to the Vichy government and made sure the authorities looked out for Stein and Toklas—even that they had coal in the winter, by his own account. But the women never cited Fa? as their savior, though they credited him with keeping their art in Paris safe from the Gestapo. After the war, Fa? was convicted of collaboration: he’d turned in Freemasons, banned under the Nazis, and thousands were imprisoned or deported—though scholars doubt how much Stein knew of his activities. She wrote a letter of support for him before his trial, and Toklas appears to have helped fund his escape from prison years later. The Stein-Toklas scholars Malcolm cites are rightly tough on their subjects; the women rarely acknowledged their Jewish roots and seemed to isolate themselves from the war’s horrors. As Malcolm puts it, “Over and over [Stein] writes of her fearfulness and helplessness in the face of the evil she cannot bring herself to imagine and yet on some level has understood.”

“Two Lives” also delves into the power play of their private relationship. We know which one wore the mustache—Toklas—but who wore the pants? Stein was the charming artist who needed constant nurturing: “It takes a lot of time to be a genius, you have to sit around so much doing nothing,” she wrote. Toklas was the housekeeper, secretary and the one who, at all their salons, sat with the wives. But Toklas was no pushover. According to one scholar, the fanatically jealous Alice—discovering that Stein once had a lover named May—made Gertrude change the verb “may” (and even the name of the month) throughout the manuscript of a poem Stein had written.

Toklas, who privately referred to Gertrude as “Baby,” was the fierce keeper of the flame after Stein’s death in 1946. Though Stein’s will was meant to care for Toklas, the estate’s trustees grabbed the paintings off the walls and sent her money in driblets. Toklas wound up penniless. She became a Roman Catholic convert, obsessed with how to make sure she met Stein in heaven. “Two Lives” is a bit disjointed but deeply engaging. It’s also a reminder that no matter how obsessively we pry, there are limits to what we can know about the lives of others.