Even for the brazenly confident Mr. Wolff, a status-mad needler with a habit of being ejected from expensive restaurants, this is a new level of notoriety. He is accustomed to angering the Manhattan power elite, not the leader of the free world. “It’s almost a natural evolution of Michael Wolff, that one day the president would be talking about him from the White House,” said Janice Min, the former editor of The Hollywood Reporter, where Mr. Wolff is a columnist.
His acidic portrayal of Mr. Trump as a president in over his head, disdained by aides who are astounded by his lack of fitness for the job, has dominated headlines and social media for days, along with his purportedly verbatim quotes from figures like Mr. Bannon and Mr. Murdoch dismissing Mr. Trump as a fool.
But Mr. Wolff has picked up as many foes as fans during his years as a slashing columnist — perhaps more, even — and critics have raised questions about the veracity of his reporting, saying that he has a history of being casual with his facts.
“Historically, one of the problems with Wolff’s omniscience is that while he may know all, he gets some of it wrong,” David Carr, the late New York Times media columnist, wrote in 2008, reviewing a Wolff book that, he pointed out, contained errors.
The excerpts from “Fire and Fury” that appeared this week have been raked over for mistakes. Mr. Wolff writes that CNN reported on Mr. Trump being accused of an exotic sexual practice with prostitutes in an intelligence dossier; in fact, BuzzFeed News reported those details. He also describes Mr. Trump as being unaware of the identity of John Boehner, the former Republican House Speaker; in fact, the pair had golfed together long before Mr. Wolff began visiting the White House.
Other details have been disputed. Thomas Barrack Jr., a close Trump friend, denied that he said the president was “not only crazy, he’s stupid,” as Mr. Wolff reports. On Thursday, the White House press secretary, Sarah Huckabee Sanders, said the book contained “mistake, after mistake, after mistake.”
Mr. Wolff, who declined to be interviewed for this article, stands by his reporting. And his publisher is apparently undaunted by the president’s threats. “We see ‘Fire and Fury’ as an extraordinary contribution to our national discourse, and are proceeding with the publication of the book,” Henry Holt said in a statement on Thursday.
Mr. Bannon has not disputed his quotes in the book, even as the material has damaged him politically and perhaps professionally: several Republican politicians have distanced themselves from him, and one of his key financial backers, the hedge fund heiress Rebekah Mercer, a funder of Breitbart, said on Thursday that she did not support his statements.
Ms. Min wrote on Twitter that she attended a dinner party that Mr. Wolff describes in detail, including a verbatim conversation between Mr. Bannon and Roger Ailes, the now-deceased former chairman of Fox News.
“Every word I’ve seen from the book about it is absolutely accurate,” Ms. Min wrote.
In a telephone interview on Thursday, she added, “People sometimes don’t like what he says, but I think one of the things that’s unnerving about Michael is he’s loyal only to the story.” Of her own collaborations with Mr. Wolff, she added, “nobody ever disputed the facts that were included on a piece.”
Raised in the New Jersey suburbs, the son of an advertising executive (his father) and a newspaper reporter (his mother), Mr. Wolff entered journalism early, as a copy boy for The New York Times. (He would later skewer The Times, along with other mainstream news organizations, as stolid and biased.) He has been a columnist and a media executive, writing a memoir about his time running a failed internet start-up, and once trying to purchase New York magazine with partners including Harvey Weinstein.
His friends say he relishes a scrap. Ms. Min recalled him grinning broadly after a party, telling her, “Everywhere I turned was someone who hated me.”
Sometimes, the spotlight has found Mr. Wolff, who became a running character on gossip websites and the city’s tabloids. His personal life caused a minor scandal after a late-life divorce, amid a relationship with a writer about 30 years his junior. (He and the writer, Victoria Floethe, now have a 2-year-old daughter.)
Mr. Wolff also became friendly with Mr. Trump, making a cameo in a pilot that never aired for a Trump-branded reality-TV project, “Trump Town Girls,” which involved beauty contestants selling real estate. After the election, he secured Mr. Trump’s trust, in part, by relentlessly criticizing other reporters’ coverage of the president-elect.
Soon, Mr. Wolff was spending days at the Hay-Adams hotel in Washington, a block from the White House, where he was routinely spotted walking into the West Wing. He dined with Trump aides at the nearby Bombay Club. His book, he writes in an author’s note, is based on about 200 interviews, including at least one conversation with the president.
“Many of the accounts of what has happened in the Trump White House are in conflict with one another; many, in Trumpian fashion, are baldly untrue,” Mr. Wolff writes. “Those conflicts, and that looseness with the truth, if not with reality itself, are an elemental thread of this book.”
Graydon Carter, Mr. Wolff’s former editor at Vanity Fair, wrote in an email that he was not surprised Mr. Wolff “would write an entertaining book.”
“The mystery,” Mr. Carter added, “is why the White House allowed him in the door.”