CNN's Jake Tapper is set to interview Comey on April 19. The Associated Press purchased a copy this week.
Comey told ABC's George Stephanopoulos that it was "possible" the Russians had material that could be used to blackmail Trump.
Should he have denied Trump's request to drop his investigation into his first national security adviser, Michael Flynn? It also includes strikingly personal jabs at Trump that appear sure to irritate the president.
"He looked slightly orange up close with small white-half moons under his eyes, which I assume are from tanning googles", Comey added. Trump seized on that, saying Comey "was making decisions based on the fact that he thought she was going to win, and he wanted a job".
The FBI director, who until his firing last May led an investigation into possible ties between Russian Federation and the Trump campaign, acknowledged that it was "stunning" to think Russian Federation could have damaging information on an American president.
He says he knows that's a "stunning" possibility and something that he never thought he'd say about a president of the United States. That meeting, just days before Comey initially said the investigation was over - became a major firestorm, with many Republicans saying it showed the former president trying to influence the outcome of the investigation in his wife's favor.
Comey also says he found out he was sacked from television reports.
Trump's firing of Comey set off a scramble at the Justice Department that led to the appointment of Mueller as special counsel overseeing the Russian Federation investigation.
Trump has assailed Comey as a "showboat" and a "liar".More news: Kathua rape case: Resignations of J&K BJP ministers accepted
More news: Saudi king slams Iran's 'interference' as Arab leaders meet
More news: Swansea City manager tips Jordan Ayew to excel in Everton clash
Despite his misgivings, Comey said he would not be in favor of impeaching Trump.
There is, of course, the supposed 'pee tape, ' but there are other allegations in Comey's salacious White House exposé.
"It is also wrong to stand idly by, or worse, to stay silent when you know better, while a president brazenly seeks to undermine public confidence in law enforcement institutions that were established to keep our leaders in check."
Comey said he initially did not pay much attention to an unscheduled meeting between Lynch and former President Bill Clinton in an Federal Bureau of Investigation airplane on the tarmac at an airport in Phoenix in June. He said Comey's book fails to answer questions about why the Justice Department didn't prosecute Hillary Clinton for using a private email server while serving as secretary of state.
Despite this, Comey told Stephanopoulos that he does not regret sending the letter. "It would depend upon other things that reflected on his intent".
He revealed new details of some of the most controversial choices of his career. While Comey does not outline the details of the information - and says he didn't see indications of Lynch inappropriately influencing the investigation - he says it anxious him that the material could be used to attack the integrity of the probe and the FBI's independence.
JAMES COMEY: I don't know what's behind that.
For the most part, Comey avoided commenting on the ongoing Russian Federation investigation.
Former Attorney General Loretta Lynch is defending her actions in the Hillary Clinton email investigation following criticism from former FBI Director James Comey.
Encounters with the president, Comey wrote, gave him "flashbacks to my earlier career as a prosecutor against the mob".
JAMES COMEY: Wow, was my reaction. I think he's morally unfit to be President.