A forthcoming book by an anonymous author identified only as "a senior official in the Trump administration" describes President Trump as volatile, incompetent and unfit to be commander in chief, according to excerpts published Thursday by The Washington Post.

The newspaper says the book tells of racist and misogynist behind-the-scenes statements by Mr. Trump and says he "stumbles, slurs, gets confused, is easily irritated, and has trouble synthesizing information."

The Post says the book "paints a chilling portrait of the president as cruel, inept and a danger to the nation he was elected to lead."

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According to the Post, the book describes Mr. Trump "careening from one self-inflicted crisis to the next, 'like a twelve-year-old in an air traffic control tower, pushing the buttons of government indiscriminately, indifferent to the planes skidding across the runway and the flights frantically diverting away from the airport."'

The Post acquired a copy of the book, "A Warning," and first reported on its contents Thursday.

White House press secretary Stephanie Grisham released a statement late Thursday saying, "The coward who wrote this book didn't put their name on it because it is nothing but lies."

She said reporters should "cover the book as what it is - a work of fiction."

In the book, due out Nov. 19, the writer claims senior administration officials considered resigning as a group last year in a "midnight self-massacre," but ultimately decided such an act would do more harm than good.

CBS News has learned that, in the book, Anonymous claims top White House staffers thought Vice President Pence was prepared to sign a letter invoking the 25th Amendment, which allows the president to be removed from office if he's deemed unable to perform his job.

But while campaigning in New Hampshire Thursday, Pence denied it, saying, "Those rumors, I dismissed them several years ago and I'm happy to dismiss them without qualification today."

On Monday, the Justice Department sent a letter to the book's publisher and the writer's literary agency, raising questions over whether any confidentiality agreement had been violated and asking for information that could help reveal the author's identity.

The publisher, Hachette Book Group, responded by saying it would provide no additional information beyond calling the author a "current or former senior official."

"A Warning" was written by the same official who wrote an opinion piece published last year in The New York Times alleging that numerous people in the government were resisting Mr. Trump's "misguided impulses."

According to the Post, the author now writes, "Unelected bureaucrats and Cabinet appointees were never going to steer Donald Trump the right direction in the long run, or refine his malignant management style. He is who he is."