Michael M. Thomas, an acerbic columnist and novelist who wrote chiefly about money and how people got it, what they did with it and what it did to them — people he dismissed as “social climbers, stock market papermongers, real estate shills and assorted other virtuosos of hype and blather” — died on Aug. 7 in Brooklyn. He was 85.

He was being treated in a hospital for complications of arthritis and died of a bacterial infection, his wife, Tamara Glenny, said.

Mr. Thomas, who was the scion of an old-line family and who inhabited the upper echelons of Manhattan society, had three distinct careers: assistant curator of European painting at the Metropolitan Museum of Art, investment banker at Lehman Brothers and, finally, writer. While he loved art history and immersed himself for a time in the world of high finance, it was with his pen — dipped, some said, in an inkwell of acid — that he found his groove.

Over nearly four decades, he turned out nine novels, most of them financial thrillers, as well as hundreds of newspaper and magazine columns and articles. His overarching theme was the pursuit of wealth, and his subplots included the enduring clash between old money and new.

“Michael came from money, and he made money,” Graydon Carter, co-editor of the digital weekly Air Mail, who worked with Mr. Thomas at Vanity Fair, Spy magazine and elsewhere, said by email. “As a result, he could write about people who came from money and made money like a modern-day Trollope.”

Many of Mr. Thomas’s characters, like Trollope’s, were obsessed with power and prestige, subjects that Mr. Thomas examined with anthropological zeal against the backdrop of a corrupt Wall Street, where the bad guys weren’t just bad but pathologically venal.

Some of his books — including his first novel, “Green Monday” (1980), in which a group of Arab oil magnates schemes to take over the United States — became best sellers and were praised for their realism.

His second novel, “Someone Else’s Money” (1982), told the story of a Texas billionaire who is dying and wants to leave his social-climbing wife a magnificent art collection. Referring to Mr. Thomas’s familiarity with the art world and Wall Street, the economist Robert Lekachman wrote in The New York Times Book Review, “Thomas knows both these environments intimately enough to detest most of the characters he has drawn, one suspects, from living models.”

While his early books received good reviews, they “are said to have been extremely unkind to the rich and fashionable,” Charlotte Curtis, a New York Times columnist and longtime observer of high society, wrote in 1985. And his magazine articles, she added, “are said to have indulged in gratuitously cruel people-bashing.”

For those reasons, Ms. Curtis wrote, Mr. Thomas became a pariah among New York’s elite. But he didn’t much care.

“They are dreadful people,” he told her. “Why shut your eyes to the truth?”

One of his novels, “Hanover Place” (1990), a tale of greed and anti-Semitism among Wall Street traders, was criticized by some as being anti-Semitic itself. Mr. Thomas was outraged by the accusation and attributed that perception to his characters’ authenticity. He then used his “Midas Watch” column in The New York Observer to take personal aim at one critic, Judith Martin, also known as Miss Manners, for her critical review in The Times: “She is a nice Jewish person who seems in her youth to have been transfixed with things WASPy.”

Mr. Thomas often used his Observer column, which ran for more than 20 years, to settle such scores. At the same time, he also wrote a column for Manhattan,inc. in which he developed a beat that he called “the new tycoonery.”

After a shouting match with Jane Amsterdam, the Manhattan,inc. editor, over changes he didn’t want to make to a column, he quit after two years and went on to write for other magazines, including Esquire, New York, The New York Times and Vogue, as well as various golf and travel publications.

Apart from his own firsthand experience on Wall Street and in the rarefied realms of the moneyed class, Mr. Thomas, who lived in homes with books stacked floor-to-ceiling, was inspired by the works of Charles Dickens.

Mr. Thomas read “Little Dorrit,” in which Dickens skewers institutions like debtors’ prisons, in 1970, when he was still a financier. He was so enthralled that he named one of his daughters Dorrit. He also found that novel to be “more fascinating and more to the point than any financial deal” and said it convinced him that high finance could make for compelling fiction. He tried his hand at it and produced “Green Monday.”

That book “has verve and a stimulating audacity,” Christopher Lehmann-Haupt wrote in a review in The Times. “It gets your back up and it keeps you awake.”

Michael Mackenzie Thomas was born on April 18, 1936, in Manhattan. His father, Joseph A. Thomas, was an investment banker who became a partner at Lehman Brothers before he was 30. His mother, Elinor (Bangs) Thomas, who traced her lineage to the Mayflower, later became a real estate broker.

Michael grew up on the Upper East Side and attended the Buckley School, Phillips Exeter Academy and Yale, from which he graduated with a degree in art history in 1958.

After teaching at Yale for a year, he landed the assistant curator job at the Metropolitan Museum. Opening the door for him was Robert Lehman, the chairman of Lehman Brothers, who was also a major art collector and who later became chairman of the Met’s board of trustees.

After a couple of years, Mr. Thomas decided he wanted to be an art dealer, but his father opposed the idea, Ms. Glenny, his wife, said in an interview. Mr. Thomas turned to Mr. Lehman for advice, and Mr. Lehman encouraged him to join Lehman Brothers. The firm hired him behind his father’s back, “which was definitely odd,” Ms. Glenny said, adding that her husband and his father had a difficult relationship.

Michael Thomas became a general partner at Lehman in 1967 and head of mergers and acquisitions in 1971. But he found the work distasteful, and he soon quit.

“I believe working on Wall Street is the most degrading form of activity that one could imagine,” he told The Washington Post in 1990. Pressed as to whether he was forced out, he added: “By the time I left, my heart was no longer in it. I was no use to them. I walked close to the edge, and maybe someone gave me a little nudge.” He also noted that he had spent quite a bit of time drinking and carousing.

He briefly ran his own financial consultancy, which he named Marshalsea Associates, after the prison in “Little Dorrit.” He worked there until he began writing full time. From 1978 to 1992 he also owned a record store on Lexington Avenue, Orpheus Remarkable Recordings, which specialized in classical and jazz.

Mr. Thomas was married four times; his first three marriages ended in divorce.

He married the actress Brooke Hayward, a daughter of Margaret Sullavan, the actress, and Leland Hayward, the agent and theatrical producer, in 1956. They had two sons, Jeffrey and William. He married Wendell Adams, a model, in 1960; they had a son, Michael, and two daughters, Leslie Thomas and Dorrit Morley. With his third wife, Barbara Siebel, a painter whom he met after mistakenly boarding the wrong flight to San Francisco and married in 1982, he had one son, Francis Thomas.

In addition to his wife, Ms. Glenny — a translator and editor at the United Nations, whom he met online in 2003 and married in 2014 — his children all survive him. So do seven grandchildren and Ms. Glenny’s two sons and a daughter from an earlier marriage, Sam, Mickey and Margie Ehrlich.

Mr. Thomas published his last novel, “Fixers,” about a conspiracy between Wall Street and the president of the United States to create a global financial meltdown, in 2016.

He also kept his hand in art projects. As a trustee of the Robert Lehman Foundation, he helped prepare and publish a scholarly catalog of Mr. Lehman’s vast art collection at the Met. The catalog ran to 15 volumes and took several decades to complete; the final volume was published in 2015.

Mr. Thomas left his own extensive collection of art books to Brooklyn College.