"I never understood half of the president's staffing", he said.
The book, released Friday by publisher Henry Holt, has already sold out at some area bookstores. "The need for immediate gratification".
In 1981, Reagan became the oldest person to begin a first presidential term, at age 69.
The president remarked on the book when asked why he felt it was necessary to have posted a message on Twitter defending his intellect.
Limbaugh, a longtime Trump ally, described Bannon, whose relationship with Trump publicly imploded this week after he was extensively quoted deriding the president and his family in "Fire and Fury: Inside the Trump White House", a new book by journalist Michael Wolff, as a creation of wealthy Republican donors. So it's - it becomes, from day one, the crisis of the presidency.
Trump, upon hearing of the book's release, expressed his views on Michael Wolff and political figure Steve Bannon.
Trump reportedly displayed more troubling behavior, such as attempting to "barricade himself" in his own bedroom. The US President has also threatened lawsuits against Wolff and Bannon. Just before its publication, Murdoch publicly questioned some of Wolff's reporting in that book.
The White House press secretary said the author of the book, contrary to the claims, had no access to the White House or the president. Seriously, how does anyone say something like that with a straight face and not go home, slip into a hot bath and slit their wrists in humiliation? We're going to Camp David.
Mr Wolff however insisted that he "absolutely" spoke to the president, adding whether he "realised it was an interview or not, I don't know, but it was certainly not off the record". "But I will tell you, they said it", he said.
As someone who loves to read, and wishes more Americans did, too, this is a trend I'd like to see more of in 2018. It should be in stores everywhere by Tuesday.
Here, arguably, was the central issue of the Trump presidency, informing every aspect of Trumpian policy and leadership: He didn't process information in any conventional sense.