In the upcoming memoir, former FBI deputy director Andrew McCabe details deputy attorney general Rod Rosenstein’s upset at allegedly being asked by the White House to draft a now notorious memo in which he advised Mr Comey’s removal.
Mr McCabe writes how, in a private meeting with Mr Rosenstein after the firing in May 2017, the 54-year-old appeared “glassy-eyed” and emotional.
“He said it wasn’t his idea. The president had ordered him to write the memo justifying the firing,” writes Mr McCabe, who added Mr Rosenstein was having trouble sleeping after concluding he had been scapegoated by the White House.
“There’s no one here that I can trust,” he quotes the deputy attorney general as saying.
The book, The Threat: How the FBI Protects America in the Age of Terror and Trump, of which an advance copy was obtained by The Guardian, is due on sale later this month.
Publicly, Mr Rosenstein has defended the memo, which criticised Mr Comey’s handling of an FBI investigation into former presidential candidate Hillary Clinton’s use of a personal email account.
In testimony to congress last year, Mr Rosenstein sided with the White House’s version of events, when he said of the memo: “I wrote it. I believe it. I stand by it.”
But when it was used as justification by Mr Trump to fire Mr Comey, Mr Rosenstein reportedly threatened to quit.
The president would later refer to “the Russia thing” as a reason for forcing out Mr Comey, who was overseeing the FBI when it was investigating potential links between the Trump campaign and Russia.
Days after Mr Comey’s dismissal, Mr Rosenstein would appoint Robert Mueller, the special counsel, to take over the FBI’s investigation – a decision that publicly infuriated Mr Trump.
Elsewhere in his book, Mr McCabe accuses Mr Trump of unleashing a “strain of insanity” into public life, and of having acted like a mobster when he allegedly offered to support Mr McCabe in return for loyalty.
“The president and his men were trying to work me the way a criminal brigade would operate,” Mr McCabe writes of his brief period as acting FBI director, according to The Guardian.
Mr McCabe would later be fired – just 26 hours before he was scheduled to retire – by then-attorney general Jeff Sessions, who alleged Mr McCabe “made an unauthorized disclosure to the news media and lacked candor”.
“Andrew McCabe FIRED, a great day for the hard working men and women of the FBI – A great day for Democracy,” Mr Trump tweeted about the sacking last year.