Fire and Fury: Inside the Trump White House by Michael Wolff:
Almost all the professionals who were now set to join him were coming face to face with the fact that it appeared he knew nothing. There was simply no subject, other than perhaps building construction, that he had substantially mastered. Everything with him was off the cuff. Whatever he knew he seemed to have learned an hour before—and that was mostly half-baked. But each member of the new Trump team was convincing him—or herself otherwise—because what did they know, the man had been elected president. He offered something, obviously. Indeed, while everybody in his rich-guy social circle knew about his wide-ranging ignorance—Trump, the businessman, could not even read a balance sheet, and Trump, who had campaigned on his deal-making skills, was, with his inattention to details, a terrible negotiator—they yet found him somehow instinctive. That was the word. He was a force of personality. He could make you believe.