Former Federal Bureau of Investigation director James Comey's new book, A Higher Loyalty: Truth, Lies And Leadership, has already turned into a best-seller even before its official release on Tuesday. Here are some of the key revelations based on excerpts leaked by US media:
Mr Donald Trump asked Mr Comey to help debunk lewd allegations made in the Trump-Russia dossier
Mr Comey described two conversations in January last year with Mr Trump in which the President sought his help to knock down an unverified report alleging that Mr Trump had been caught on video with hired prostitutes and had watched them urinate on a bed in a Moscow hotel room in 2013.
The allegations had been contained in a document compiled by a former British intelligence officer.
Mr Trump said the story was untrue and was distressing to his wife Melania. He also insisted that it was unlikely because he was a self-professed germophobe. Mr Comey said Mr Trump strongly denied the allegations, even asking whether the President "seemed like a guy who needed the service of prostitutes". Mr Comey said the conversation went on until he finally said: "'We are not investigating you, sir.' That seemed to quiet him."
Meetings with Mr Trump reminded Mr Comey of his work against the mob
Mr Comey, a veteran law enforcement agent, writes unsparingly about Mr Trump, calling him a tempestuous President whose connection to honesty was tenuous at best.
He said his service to Mr Trump recalled for him the days when he investigated the mob in New York as a prosecutor. He described it at length as: "The silent circle of assent. The boss in complete control. The loyalty oaths. The us-versus-them worldview. The lying about all things, large and small, in service to some code of loyalty that put the organisation above morality and above the truth."
Mr Comey offers searing criticism of the "forest fire" that is Mr Trump's presidency
The book paints a devastating portrait of a President who built "a cocoon of alternative reality that he was busily wrapping around all of us", Mr Comey wrote.
"We are experiencing a dangerous time in our country," he wrote, "with a political environment where basic facts are disputed, fundamental truth is questioned, lying is normalised and unethical behaviour is ignored, excused or rewarded."
Mr Comey defends his handling of the Clinton e-mail investigation
Mr Comey was denounced by many Democrats for announcing less than two weeks before the 2016 election that the FBI was examining a new trove of e-mails belonging to Mr Trump's rival Hillary Clinton - a move many Democrats blamed for Mr Trump's victory. Mrs Clinton had been under probe for compromising classified information by using a private e-mail system.
In the last days of the campaign, however, Mr Comey said the FBI maintained that Mrs Clinton should not face criminal charges over the e-mails.
In his defence, Mr Comey acknowledged that he thought Mrs Clinton would win the presidency, adding that he was concerned that if he concealed the renewed investigation, it would make her an "illegitimate president".
Former president Barack Obama offered him kind words after the Clinton probe fallout
Mr Comey detailed for the first time a private assurance he received from Mr Obama following the fallout of the Clinton e-mail saga.
Mr Comey wrote that Mr Obama sat alone with him in the Oval Office in late November 2016 and told him: "I picked you to be FBI director because of your integrity and your ability. I want you to know that nothing - nothing - has happened in the last year to change my view."
Mr Comey reveals that Mr Trump's chief of staff John Kelly offered to quit after his firing last May
Mr Comey said that after his firing, he received "an emotional call" from Mr Kelly, who was then the Secretary of Homeland Security. Mr Kelly said he intended to quit in protest.
"I urged Kelly not to do that, arguing that the country needed principled people around this President. Especially this President," Mr Comey wrote.
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