For those of us who are women of a certain age and have subscriptions to Vanity Fair, the star-crossed friendship between Truman Capote and socialite Babe Paley was the stuff of tabloid legend. They met cute in the mid-’50s when he hitched a ride on the Paleys’ private plane. When her husband, CBS titan Bill Paley, heard that “Truman” was coming, he was expecting the former president, not the flamboyant boy author. Capote soon became Babe’s favorite lunch date and weekend guest, who could be counted on for gossip, flattery and a sympathetic ear. Over the next 20 years, he became “her analyst, her pillow, her sleeping pill at night, her coffee in the morning.” She entrusted him, unwisely, with the most shameful secrets of her sexless marriage.

Like many great loves, theirs ended in a tragic betrayal. In 1975, Capote published “La Cote Basque, 1965,” an excerpt from his unfinished novel, “Answered Prayers.” Over a long, drunken lunch at the famous restaurant, Lady Ina Coolbirth shares some of the most lurid tales of her high-society friends. One is about a multimedia tycoon, Sydney Dillon, who has a squalid one-night stand and desperately tries to wash the stained bedsheet before his wife gets home. Babe, who was dying of lung cancer at the time, recognized the similarity to her husband. Capote had, literally and literarily, aired her dirty laundry; she refused to speak to him ever again.

In her highly entertaining new novel, “The Swans of Fifth Avenue,” Melanie Benjamin investigates the bonds between this mismatched pair and Capote’s self-destructive urges that eventually ruptured them. The novel’s narrative structure is a bit like wandering through La Cote Basque at lunchtime and overhearing snippets of conversation. In alternating chapters, Capote and Babe offer their own versions of their friendship. Celebrity characters also weigh in with their two cents: socialites Slim Keith and Pamela Churchill Harriman, Truman’s lover Jack Dunphy, Diana Vreeland and Bill Paley.

Benjamin has proved an able chronicler of the inner lives of women partnered to famous, narcissistic men. In her bestselling novel “The Aviator’s Wife,” the introspective narrator, Anne Morrow Lindbergh, examined her suffocating marriage to the chilly, autocratic Lindy.

But what was the inner life of Babe Paley, a woman renowned solely for her exteriors — her Vogue-model face, her best-dressed-hall-of-fame wardrobe, her exquisitely decorated homes? Benjamin looks for an answer in an oft-repeated description by none other than Capote himself: “Babe Paley has only one fault — she’s perfect. Other than that, she’s perfect.”

Born Barbara Cushing in 1915, she was raised to marry well by an ambitious mother, a goal she achieved brilliantly when she became the second wife of William Paley, the megalomaniacal founder of CBS. Benjamin portrays Babe as serving her husband with “geishalike” attention. Morning or night, she never let him see her without coiffed hair and flawless makeup. Their houses and social life clicked along on well-greased rails: the vases filled daily with fresh flowers, the refrigerators stocked with Bill’s favorite snacks, the dining table circled with amusing guests.

But to Capote, Babe confided the price she paid for such seemingly effortless perfection: “Surface, surface, surface — that was her life.” As a result of a car accident as a teenager, she had scars under that pancake makeup and “false teeth” that “ached incessantly.” She was so busy catering to Bill’s every whim that she mostly ignored her children. And she discreetly looked the other way when he pursued other women.

But what did Capote find so compelling in Babe, who wasn’t literary or even particularly witty? Benjamin suggests that he craved the trappings of great wealth after his Southern Gothic childhood cast off by a rejecting mother. Traveling first class with the Paleys to azure beaches, lunching with Babe and her fellow socialite “swans,” he felt sheltered from the “foul smells and tattered fabric” of real life. More important, Capote recognized himself in Babe: a self-invented persona who was “so goddamned lonely” underneath.

But after the publication of “In Cold Blood” and the Black and White Ball he threw at the Plaza, his writing career, along with his alcoholism, spiraled downward. With the publication of “La Cote Basque,” he managed to detonate his own life. Shunned by Babe and her friends, he became a bloated self-parody, repeating the same malicious stories in a slurring, elfin voice.

In her author’s note, Benjamin says she had more fun writing “The Swans of Fifth Avenue” than her previous novels, and it shows. The best scene in the book, the fabulous Black and White Ball told from the viewpoints of various guests, displays Benjamin’s wit and verve. Katharine Graham gets bouffanted by the famed hairdresser Kenneth; Marie Dewey, the sheriff’s wife from “In Cold Blood,” fox-trots with Rudolf Nureyev; Frank Sinatra grumpily watches Mia doing the “frug or whatever it was.”

The weakest parts of the book are, alas, the intimate scenes Benjamin imagines between Babe and Capote in the dawn of their friendship. Babe’s breathless confessions about her first kiss, her guiltiest pleasure (ice cream!), her greatest fear (“That I’ll never be loved”) make her sound cringingly tweenage. She is far more compelling as she faces her gruesome death with clear-eyed bitterness: “I’ll only be remembered as the woman who tied a goddamned scarf around her handbag one day, and sparked a national trend.”

“The Swans of Fifth Avenue” ends where it begins, during a lunch at La Cote Basque. Babe’s friend Slim Keith raises a toast that captures the lovely elegiac power of this novel: “Babe. . . . And even Truman . . . as he was, back then. Our fun, gossipy friend. Our entrée into a different world, for a time. An amusing, brief little time. A time before it was fashionable to tell the truth, and the world grew sordid from too much honesty.”

Caroline Preston’s latest novel is “The Scrapbook of Frankie Pratt.”

The Swans of Fifth Avenue

By Melanie Benjamin

Delacorte. 341 pp. $28