Author Michael Wolff said in an interview published Wednesday that his high-profile new book on the Trump White House sold a million copies in four days.

“I’m going around saying, ‘It’s just a book,’ but it has become something so much larger,” Wolff told The New Yorker in an article published on Wednesday.

"Fire and Fury: Inside the Trump White House" sent shockwaves through Washington last week after a series of controversial excerpts were published before the book's official release.

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Wolff claims that various members of President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE's staff have questioned the president's mental health and fitness for office.

The book also quotes Trump's former chief strategist, Stephen Bannon, as saying Donald Trump Jr. Don John Trump'Tiger King' star Joe Exotic requests pardon from Trump: 'Be my hero please' Zaid Jilani discusses Trump's move to cancel racial sensitivity training at federal agencies Trump International Hotel in Vancouver closes permanently MORE's meeting with a Russian lawyer at Trump Tower in 2016 was "treasonous" and that investigators would crack Trump Jr. like "an egg" on national television.

Bannon has received backlash from his past supporters and the president for the comments and has since resigned from his post at Breitbart News.

Trump and the White House pushed back on the book, calling it "pathetic" and "full of mistakes."

The White House also attempted to stop the book's publication with a cease-and-desist letter.

Wolff's attorneys called the legal threats against the author “a gross violation of the First Amendment" on Monday.