A young person who’s just moved to New York can hardly ignore the name Astor. It spans only one block, but Astor Place is frequently invoked by 23-year-olds, as it connects Broadway to St. Marks Place, the enduringly hip East Village destination. To the new New Yorker, the name Astor conjures up downtown and youth and trendiness (and Kmart, too, as it sits right there)—which is ironic, since the Astors themselves are very much an uptown crew, hardly cutting-edge and most definitely not cheap.

Brooke Astor is the last member of this famous family who will ever matter much to those of us who have said the name so often. She’s 105 years old and bedridden. Upon her death—which may still be a ways off, given her prodigious will to live—we’ll surely be treated to a doorstop biography or two. But for now, while she’s still with us, we have Frances Kiernan’s The Last Mrs. Astor, a concise and engaging look at the tiny doyenne of society who did so much good for Gotham.

Before she was Brooke Astor, the woman we know as a “living monument” (sort of a backhanded compliment, really) was married to two other men—both of whom made her wealthy. Her second husband and “love match,” Charles (Buddie) Marshall, died suddenly in 1952, after 20 years of marriage. Just 11 months later, Brooke Marshall became the third and final Mrs. Vincent Astor.

There are competing stories about her third marriage, but it seems indisputable that Brooke Marshall’s primary reason for becoming Brooke Astor was money: Her new husband had a considerable personal fortune as well as an eponymous foundation worth close to $450 million by today’s standards. It’s not that Brooke was greedy, but her means were limited, and by that point she did have a lavish lifestyle to maintain. She also seems to have been excited by the idea that she might one day run the Vincent Astor Foundation—a promise that her husband is said to have made to her before she agreed to become his wife.

Vincent died in 1959, and within two years Brooke Astor was president of the foundation. Ms. Kiernan’s book is most valuable as a catalogue of all of the things that Mrs. Astor did for us—the residents of this city—with her husband’s fortune. The New York Public Library, the Metropolitan Museum, the Bronx Zoo, Central Park, The New York Review of Books—without Brooke Astor, these institutions might not have survived some of their worst moments or, in the case of the NYRB, never have come into being. Her fingerprints are all over the city, and she seems always to have been on the side of good and right: saving historic buildings, buying books for libraries, expanding art collections.

No wonder Frances Kiernan is such an over-the-top fan. Though there are moments when she hints that Brooke Astor may have been a less-than-perfect woman, as soon as our ears prick up, we’re whisked off to another party or fund-raiser in her honor. Still, The Last Mrs. Astor is a valuable and enjoyable appreciation of a great old lady, a relic of old, rapidly disappearing New York.

Hillary Frey edits the culture pages of The Observer.

Mary McCarthy was a tactician of scandal; she had a sure sense of just how much would be good for her. She learned this early on. In her freshman English class at Vassar, students' papers were kept in a folder in the library for classmates to read; one of them, Lucille Fletcher Wallop, remembers the effect of McCarthy's compositions: "I learned from her short stories that deviled ham was fatal to a proper orgasm and that lettuce was a powerful aphrodisiac. I had never heard of orgasms or aphrodisiacs, but I lapped up her descriptions, as did the rest of the class, who often lined up in a long queue waiting for the folder."

Fifty years later, when she told Dick Cavett in a television interview that every word Lillian Hellman wrote was a lie, including "and" and "the," she didn't expect to be sued for libel; but when Herbert Mitgang first told her about the suit, the idea of the scandal didn't displease her: "I laughed," she remembered. "He said, 'You won't laugh when I tell you it's for two and a quarter million dollars.' I think I did laugh again."

Seeing Mary Plain , Frances Kiernan's semi-oral biography, is punctuated by such affairs; they are, with her books, McCarthy's gift to posterity. More: Her writing and her life converged, and were often interesting for the same reason and in the same way. The best-known facts of her biography are her lovers and her husbands; her best-known fictions are "The Man in the Brooks Brothers Shirt" and the "pessary" episode from The Group , both programmatically, scandalously honest about sex. And, of course, her novels are buckets drawn from the well of personal anecdote: The scheming professors of The Groves of Academe , the confused alumnae of The Group , all have identifiable "originals." She wrote and rewrote her memoirs several times.

All this makes McCarthy an ideal subject for an oral biography. As time passes, it becomes clearer that she was a fine writer but not a literary artist; she did not achieve (or necessarily attempt) the promotion from talk to writing, from life to work, that artists aim for, and so it is fitting that talk should memorialize her. Unfortunately, Seeing Mary Plain is not quite that memorial. It is injured, above all, by the absence of the most important voices in McCarthy's life. Ms. Kiernan writes that she began the book in the early 90's, and by that time the key witnesses were dead: Harold Johnsrud, whom McCarthy married at 21 and divorced at 23; Philip Rahv, her lover; Edmund Wilson, whom she married and suffered with to her friends' bewilderment; Hannah Arendt, her unlikely best friend; and, of course, almost everyone who knew her as a child. Others, who are still living–most notably Reuel Wilson, her son, and Bowden Broadwater, her third husband–barely participated.

Ms. Kiernan fills these gaps with dozens of more tangential observers, and with her own narrative, neither of which quite compensates. Isaiah Berlin, Saul Bellow and Alfred Kazin, none of them intimates of McCarthy, provide some of the most astute observations, especially of the scandal surrounding Eichmann in Jerusalem , which McCarthy defended out of loyalty to Arendt and, one suspects, out of a sense of where the action was. From time to time, one catches the tone of the Partisan Review crowd of which McCarthy was a founding member, the merciless, intimate, ingenious arguments. (McCarthy was especially close to the Italian intellectual Nicola Chiaromonte, of whom William Phillips recalls, "People thought he was a genius because he was silent. Because he didn't talk much. He felt a lot.")

Inevitably, most of the people who are still around to be interviewed are much younger than McCarthy, and knew her in her more placid last decades; they are not peers but students, admirers, secretaries, even a maid. As a result, the second half of the book feels much too long, with details of McCarthy's houses and travels and finances and health squeezing out matters literary and genuinely personal. There are suggestions, for instance, that her relationship with her son was strained (he failed to attend her funeral), but the cause of the breach is not made clear.

Given the shortage of "raw material," the other possible approach for Ms. Kiernan would have been a close psychological analysis, an attempt to find out what made McCarthy so attractive and difficult. The theme that runs through her life and work is total certainty; she looked on tempests domestic and political and was never shaken. This made her formidable in conversation, where she delighted in holding people's characters up for evaluation, and extremely seductive to the people–usually men–on whom she focused her attention. It was also her major flaw as a writer, of both fiction and nonfiction. In The Group , for instance, one always feels sorry for McCarthy's characters, summoned out of the ether to be ridiculed and condescended to by their superior author.

In her two books of Vietnam reportage, the same certainty, transposed to the political realm, makes her come off as shamefully, irresponsibly naïve: She is led around by the nose by the North Vietnamese, whom she trusts implicitly, while she mocks an American prisoner of war. Ms. Kiernan's account of her meeting with that P.O.W., and its aftermath–after his release, he wrote about how McCarthy had "knocked on wood" during their meeting, leading him to be interrogated for hours about the code she must be using–is a locus classicus of the irresponsibility of the intellectual.

The fruitful question is what experiences and drives led McCarthy to place such value on being always and in advance correct, and superior to everyone around her. Ms. Kiernan goes some way toward an answer in her sketch of McCarthy's childhood, which is like something out of a fairy tale, minus the happy ending: After an idyllic early childhood with her charming, young parents, she was orphaned by the flu epidemic of 1918 and sent to live with old, humorless, abusive relatives. (When McCarthy came home one day with a school prize, her uncle beat her with a razor strop–"to teach me a lesson, he said, lest I become stuck-up"). The shock of that change would have been enough to make her realize that she had to be always self-sufficient, always able to master the people and circumstances around her. Her strangely cold obsession with sex–as Susan Sontag observes, her attitude seems to be that "when [men] do it with you, you have something on them"–is another form of this wary mastery. One does not have to be a Freudian (and McCarthy had no use for Freud) to guess at some sort of early sexual trauma. In The Group , the character whose life most resembles McCarthy's ends as a suicide; the most idealized character, the dream-Mary, turns out to be a lesbian.

An intrepid biographer could make much of this. But Ms. Kiernan, ensnared by her method, is confined to recounting events and bridging quotes. The result is that much of McCarthy's brilliance, charm and force are leached out. Ms. Kiernan's book gives us Mary plainer than she was.