These connections prove as formative, if not more so, than many of her relationships with men, which are a side element of this remarkably written — if occasionally uneven — book. These female guides are not benign or consistently benevolent — there are no pure or magical muses here, no easy plots or expected fixes. The women who populate Sonnenberg’s universe are feisty, edgy, problematic, fantastic, sexy, ambitious, secretive, neurotic, playful, intelligent, big-hearted, and fierce; in other words, they act as mirrors for the author herself, who becomes alternatively strange and recognizable to herself and to her reader through relationships that range from antagonistic, mutually supportive, “vital and exquisite and symmetrical,’’ sisterly, loving, sometimes sexual, worshipful, and in most cases, redemptive in some significant way.

Deep specificity in a memoir serves universal meaning because it drops the reader into the lives and minds of the characters. This is certainly true in “She Matters’’; each of Sonnenberg’s guides is exquisitely rendered in an almost deliciously obsessive way — we see each woman’s home, her habits of dress and gesture and speech, her movements through space, and these details make each woman somehow iconic.

Sonnenberg captures the closeness between women friends that occasionally moves into periods of “doubleness.” Each initial encounter reads like the opening of a new love story. “I mimicked the flutter in her face, imitated her cadences, as if I might enchant myself and transform into her, which would demonstrate how deeply I knew her.”

Another great strength of the book is Sonnenberg’s dogged willingness to self-implicate. Without restraint she reveals herself in all her neediness, jealousy, compassion, almost manic desire to be loved in the wake of a mother (the subject of Sonnenberg’s first book, “Her Last Death”), who taught her that the primary task in any relationship is to eventually burn it down. “I lunged for intimacy, for the reassurance — I like you! do you like me? — but I always grabbed for it too soon, thinking that a lot equaled intimacy, and ‘a lot’ never seemed like enough anyway. This made the girl quickly awful, at once too significant, and it probably made me awful to them, my alarming, unexplained hungers. We ignited, large, and flamed out.”

In one scene she tells a friend struggling with the challenges of new motherhood, that she is a bad mother. She lets a true friend down by judging her life choices and lacking the courage, until much later, to apologize. She not only catalogs moments when she was betrayed or disappointed by a girlfriend, but shows herself as petulant and withholding, wild and disloyal, afraid to give but willing to take, and readers will admire, and relate to, this penetrating honesty.

Sonnenberg makes the important point (not to mention a very feminist one) that women support, forgive, fight, and sustain one another, often over the course of decades-long friendships, sometimes during just the span of a single day. Friendship between and among women generally is not easy, frivolous, or uncomplicated. But it is, as Sonnenberg makes quite clear, absolutely essential.

In one chapter the author helps a friend declutter a house of “the fine litter of memory.” She describes an early roommate relationship as one in which “[w]e played at every realm at once: house, family, seduction, education, marriage, united effort.” Later, a much younger woman takes Sonnenberg through a ritual that enables her to forgive herself for a difficult decision she made years earlier.

Although Sonnenberg is a gifted literary stylist with a stunning ability to write sentences that read like beautiful traps, the book’s tone is often uneven, and sometimes the language is overwrought in a way that undermines the profound nature of the author’s experiences. For example, one moment when Sonnenberg talks about the “bigness of sex,” or friendships designed solely to “save the mothers.”