Drawing heavily on reporting by The New York Times, Mr. Stewart, a Times reporter, also fleshes out how Mr. Rosenstein raised with Mr. McCabe the possibility of invoking the 25th Amendment, which allows a vice president and a majority of cabinet members to remove an unfit president from office. In a new detail, he wrote that Mr. Rosenstein told Mr. McCabe during a May 16, 2017, meeting that Attorney General Jeff Sessions and John F. Kelly, the homeland security secretary, would most likely support such a move.

“At times he got up and walked around the table,” Mr. Stewart wrote of Mr. Rosenstein during the meeting in the deputy attorney general’s office. “At one point, he was so upset he went into an adjoining bathroom to compose himself.”

That evening, Mr. Rosenstein revealed that Mr. Trump wanted Mr. Kelly to run both the F.B.I. and the Department of Homeland Security as part of a “strategy for disruption,” according to the book. “You’ve got to be kidding,” Mr. McCabe told him.

For his part, Mr. Kelly was deeply disturbed by Mr. Comey’s ouster. He called Mr. Comey as soon as he learned of it, saying that “he felt sickened by Trump’s decision to fire him and wanted to quit in protest,” the book said. “He didn’t want to work for someone so dishonorable.”

Those reservations were apparently short-lived: Mr. Kelly went on to serve as Mr. Trump’s chief of staff for 17 months.