Asked to clarify what he meant when he wrote that Mr Trump’s entire circle questioned his fitness for office, Wolff said, “100 per cent of the people around him … they all say he is like a child”.
“My credibility is being questioned by a man who has less credibility than perhaps anybody who’s ever walked on Earth.”
On Thursday evening, Mr Trump tweeted, “I authorized Zero access to White House (actually turned him down many times) for author of phony book! I never spoke to him for book.”
“Full of lies, misrepresentations and sources that don’t exist,” he added.
The early excerpts have also caused a public rift between the President and his former chief strategist and top campaign aide, Steve Bannon, over Mr Bannon’s comments in the book about Mr Trump and his family.
In Washington, customers lined up in bitterly cold weather to purchase a copy at KramerBooks, which began selling copies at midnight.
Many Washington-area bookstores, including KramerBooks, reported selling out of copies as of Friday morning at 10:00am.
Justin Bethel, manager of the Politics and Prose bookstore, said its 30 copies sold out quickly.
The reaction was less frenetic in New York, Mr Trump’s old home base. Book Culture, an independent book seller in the Upper West Side neighbourhood, said on Friday morning four people had bought the book and it had about 160 copies available, with 150 copies available in its other store.
Media player: “Space” to play, “M” to mute, “left” and “right” to seek.
White House spokeswoman Sarah Sanders, who has called the book trash, said again on Friday that Wolff had talked only briefly to the President and did not have wide access.
“This is a guy who made up a lot of stories to try to sell books,” Ms Sanders said in an interview on Fox News Channel.
In a tweet on Friday, Mr Trump called the book another attempt to smear him since any collusion between his election campaign and Russia “is proving to be a total hoax”.
Well, now that collusion with Russia is proving to be a total hoax and the only collusion is with Hillary Clinton and the FBI/Russia, the Fake News Media (Mainstream) and this phony new book are hitting out at every new front imaginable. They should try winning an election. Sad!