UPDATE with Trump tweet “He’s lost it.” So said Michael Wolff, bluntly, about President Donald Trump – more specifically, about Trump’s mental fitness for the job – on the Fire and Fury author’s first TV appearance to promote the hottest thing in a very cold winter.

Watch the entire interview below.

Just two hours before the rushed, 9 a.m. ET release of the Holt & Co. book this morning, Wolff appeared on NBC’s Today, and he showed no signs of giving the tweeting president any edge.

“Where do I send the box of chocolates?” Wolff told Today‘s Savannah Guthrie about the cease and desist letter Trump sent the author and his publisher yesterday. “Not only is he helping me sell books, but he’s proving the point of the book.”

Later this morning, Trump hit Twitter to call the book “phony” and castigate “the Fake News Media” (which he qualified with the parenthetical “Mainstream”) and Hillary Clinton, and asserted that “collusion with Russia is proving to be a total hoax…”

Last night, Trump tweeted that the book was “Full of lies, misrepresentations and sources that don’t exist. Look at this guy’s past and watch what happens to him and Sloppy Steve!” The latter apparently is Trump’s new nickname for the man who was once his chief strategist and most important political guru, Steve Bannon.

Trump also claimed, in the tweet, that he “authorized Zero access to White House (actually turned him down many times)” regarding Wolff’s seemingly near-unrestricted access to White House staffers.

On Today, Wolff responded, “What was I doing there if he didn’t want me to be there?” The author said he spoke to the president for about three hours over the course of the campaign and in the White House (“whether he realized it was an interview or not I don’t know, but it was not off the record”).

“The point of the book is I spoke to the people who spoke to the president on a daily, sometimes minute-by-minute basis,” Wolff said. “In a sense there was one question on my mind when I began this book – What is it like to work with Donald Trump, how can you work with Donald Trump, and how do you feel having worked with Donald Trump?”

Wolff said he has notes and recordings of various interviews – he didn’t specify which ones or how many – and that he’s “comfortable with everything I have reported in this book.”

“My credibility is being questioned by a man who has less credibility than perhaps anyone who has ever walked on earth at this point,” Wolff said about Trump’s overnight tweet.

One of the book’s themes that’s emerged during the pre-publication media frenzy is Trump’s mental acuity and fitness for the job, and Wolff didn’t dance around the issue today, claiming that “100 percent of the people around him” question his intelligence.

“They say he’s a moron, an idiot. Actually there’s a competition to sort of get to the bottom line here of who this man is. This man does not read, he does not listen, he’s like a pinball just shooting off the sides.”

And, Wolff said, “They all say he is like a child, and what they mean by that is he has a need for immediate gratification, it’s all about him.”

More troubling, Wolff said Trump’s habit of repeating himself in conversations has recently increased, with the repetitions occurring within “a shortened period of time.”

“I will quote Steve Bannon,” Wolff said. “He’s lost it.”