Throughout, Hauser weaves in ­passages connecting Brown to her contemporaries and the cultural landscape of the 1960s. These side glances not only help situate her life in the context of its times. They remind us of how many of her stances were truly progressive — her vocal support of access to contraception and legal abortion, for instance. They also offer amusing glimpses into friendships and catty contretemps. We learn that Hugh Hefner was an early ally and that Gloria Steinem was often dismissive. Joan Didion was agnostic. A 1965 profile by Didion, published in The Saturday Evening Post, observed that Brown seemed mostly “very tired.”

Gerri Hirshey’s “Not Pretty Enough” presents a narrower, but deeper, perspective. As Hirshey states in her introduction, her book is concerned more with the character and psychology of its protagonist than with her cultural surroundings. Where Hauser’s method is montage, Hirshey suggests her own approach is ­“pointillist.”

“Not Pretty Enough” begins with contemporary reminiscences before it dissolves, like a classic Hollywood flashback, to 1893, when Brown’s mother, Cleo Sisco, was born in the Ozarks. Brown’s father died in a freak elevator accident in June 1932, when Helen was only 10 and her sister, Mary, was 14. Their childhood was impoverished and itinerant. Cleo moved her daughters across state lines several times before settling in Los Angeles and remarrying. Mary was afflicted by polio, while Helen suffered from disfiguring acne.

Hirshey makes a strong case that the “intimate rituals of utter frustration and despair” that Brown shared with her hapless mother, along with her idealization of her dead father, shaped her forever. Indeed, they may have shaped the entire Cosmopolitan empire: “Cleo’s basic self-improvement message was a dour version of the one Helen would banner with big-sisterly cheer in her own best sellers and in her magazine: Honey, do the best with what you have.”

Hirshey’s psychological insights into Brown’s childhood, as well as the book’s treatment of Brown’s long partnership with her husband, deepen and complicate the plucky image that Brown projected in public. Given how fixated she was on the connections between sex appeal and success, it’s unsurprising she struggled as she got older. After her death, Brown was treated with the special cruelty that our culture reserves for women who do not know when to desist from trying to be desirable. Even her obituary in The Times included a snide remark: “She was 90, though parts of her were considerably younger.”

Hauser speeds over Brown’s twilight, when she turned into a grim caricature of herself, the emaciated octogenarian in fishnets doling out oral sex tips and saying reprehensibly ignorant things about H.I.V. and sexual harassment. “For all her confessions,” Hauser concludes, “Helen remained unknowable, even to those who knew her best.”

Hirshey lingers over the denouement, taking several chapters to chronicle Helen’s later years as the editor of Cosmopolitan’s international editions, her declining health, her late-in-life weight gain and her stunned grief after the death of David. When people asked how she was dealing with it, she offered a pantomime of nonchalance that sounds like a kind of despair: “Well, I come to work every day.”