The 300-plus-page book, "A Higher Loyalty," is set to be released next week. But the Washington Post and the Associated Press have published a series of excerpts ahead of schedule.
Comey, who was fired by Trump in May 2017, said he wrote detailed notes about his experiences with Trump after each of their few interactions.
The White House did not immediately respond to CNBC's request for comment on a number of Comey's statements from the book.
Here are some of the most revealing things Comey wrote about Trump:
- Trump brought up the most lurid allegations from the now-infamous Trump-Russia dossier — again and again: In a January 2017 conversation, Trump denied that he had been involved with prostitutes in a Moscow hotel in 2013, "Asking — rhetorically, I assumed — whether he seemed like a guy who needed the service of prostitutes. He then began discussing cases where women had accused him of sexual assault, a subject I had not raised. He mentioned a number of women, and seemed to have memorized their allegations."
- In a follow-up call on Jan. 11, Trump argued that the allegation couldn't be true because "I'm a germaphobe" and "There's no way I would let people pee on each other around me. No way."
- Trump brought it up again on March 30: "For about the fourth time, he argued that the golden showers thing wasn't true, asking yet again, 'Can you imagine me, hookers?'"
- Comey describes Trump as being "untethered to the truth" and appears to allude to Trump when writing about the psychology of liars: "They lose the ability to distinguish between what's true and what's not," Comey writes. "They surround themselves with other liars . . . Perks and access are given to those willing to lie and tolerate lies. This creates a culture, which becomes an entire way of life."
- When then-Director of National Intelligence James Clapper briefed Trump and his team about the intelligence community's findings on Russian election meddling, Comey said Trump's team "had no questions about what the future Russian threat might be." Rather, they brainstormed how to "spin what we'd just told them" for the public.
- Trump thought he gave "a really great answer" when he told ex-Fox News host Bill O'Reilly, who had called Russian President Vladimir Putin a "killer," that "there are a ton of killers. We've got a lot of killers. What do you think? Our country's so innocent?"
- Comey said Trump complained to him about the media response to his answer, saying: "Really, it was a great answer. I gave a really great answer."
- Comey writes that after Trump fired him, Homeland Security Secretary John Kelly (who has since become Trump's chief of staff) called him and said that "he was sick about my firing and that he intended to quit in protest."
- "He [Kelly] said he didn't want to work for dishonorable people who would treat someone like me in such a manner," Comey writes in the book. "I urged Kelly not to do that, arguing that the country needed principled people around this president. Especially this president."