The book is full of Clinton focusing blame elsewhere, but in raw terms -- and with more directness than at any point since Election Day -- the former Democratic nominee admits that she made catastrophic mistakes during the campaign that led to her loss.
"I've tried to learn from my own mistakes," she writes in her author's note. "There are plenty, as you'll see in this book, and they are mine and mine alone."
Clinton's admissions will likely be well received by Democrats who have wanted to hear her -- in unequivocal terms -- admit that she made mistakes that led to Trump's win. Many of those Democrats have been angered by Clinton equivocating at public events across the country about why she lost.
But even as Clinton cops to her failures in direct terms in "What Happened," her admissions are not unequivocal.
Here are the mistakes Clinton admits she made:
Her 'damn emails'
Clinton labels her decision to use a private email server as secretary of state -- and the subsequent investigations that led to nonstop stories -- as a "boneheaded mistake" that "turned into a campaign-defining and --destroying scandal."
Clinton says that the primary effect of the email controversy was that it repeatedly knocked her off her campaign message and left voters thinking that, once again, controversy was hanging over a Clinton vying for office.
"The controversy over my emails quickly cast a shadow over our efforts and threw us into a defensive crouch from which we never fully recovered," Clinton writes.
The former first lady says that the media made far too much out of the email controversy -- "The dumb decision by one presidential candidate to use a personal email account at the office ... got more coverage than any other issue in the whole race" -- leaving voters feeling like it was the most important issue of the campaign.
But she does say that she owns her email issue.
"Right off the bat, let me say again that yes, the decision to use personal email instead of an official government account was mine and mine alone. I own that. I never meant to mislead anyone, never kept my email use secret, and always took classified information seriously," Clinton writes.
Not understanding the electorate
Clinton's most introspective critique in "What Happened" is that she didn't fully understand the 2016 electorate and was the wrong candidate for the tone of the country.
Clinton has repeatedly said she didn't think she would lose when she settled into her hotel suite on Election Night. But after extensive reflection -- which she called "excruciating" -- she realized that she may have been the wrong kind of candidate for an electorate that wanted anger and outrage.
"Still, in terms of fighting the previous war, I think it's fair to say that I didn't realize how quickly the ground was shifting under all our feet," Clinton writes. "I was running a traditional presidential campaign with carefully thought-out policies and painstakingly built coalitions, while Trump was running a reality TV show that expertly and relentlessly stoked Americans' anger and resentment."
Clinton said her 2016 campaign forced her to face her fears of her limitations as a candidate and the lessons she failed to learn from the 2008 campaign. But, in the end, she was "unable to connect with the deep anger so many Americans felt or shake the perception that I was the candidate of the status quo. And look what they'd thrown at me."
"I go back over my own shortcomings and the mistakes we made," she writes. "I take responsibility for all of them. You can blame the data, blame the message, blame anything you want -- but I was the candidate. It was my campaign. Those were my decisions."
The comment reverberated throughout Appalachia. Republicans seized on it and, as Clinton writes, the comment became the gaffe she regrets most.
"You say millions of words in a campaign and you do your best to be clear and accurate. Sometimes it just comes out wrong," she writes. "It wasn't the first time that happened during the 2016 election, and it wouldn't be the last. But it is the one I regret the most. The point I had wanted to make was the exact opposite of how it came out."
The comment led Clinton to headline a multi-day bus tour through virulently anti-Clinton areas in Kentucky, West Virginia and Ohio, leading to what became a hostile confrontation in Williamson, West Virginia, where several hundred protesters greeted her with "Go home Hillary" signs.
"I knew I wouldn't get a warm welcome in West Virginia," she writes. "But this level of anger took me aback. This wasn't just about my comments in one town hall. This was about something different."
Letting Comey go
Clinton would like a do over on her response to James Comey's July news conference, where the FBI director accused Clinton of being "extremely careless" in how she handled her emails.
"My first instinct was that my campaign should hit back hard and explain to the public that Comey had badly overstepped his bounds -- the same argument Rod Rosenstein would make months after the election," she writes, referencing the letter Trump's deputy attorney general wrote to justify firing Comey.
Unnamed people on Clinton's team, however, "raised concerns with that kind of confrontational approach," Clinton recalls.
"In the end, we decided it would be better to just let it go and try to move on," Clinton writes. "Looking back, that was a mistake."
Pushing back against the media
Clinton has plenty of criticism for the media throughout this book, but she specifically cites NBC's Matt Lauer's performance during the Commander-in-Chief Forum in September 2016.
Clinton mocks Lauer's focus on her use of a private email server for the bulk of the forum, moments before he would "soft-pedal Trump's interview."
"Trump should have reported his performance as an in-kind contribution," Clinton writes.
But the exchange also left Clinton regretting how she handled the moment.
"Here's another example where I remained polite, albeit exasperated, and played the political game as it used to be, not as it had become," she said of her decision not to confront Lauer on air. "That was a mistake."
'Basket of deplorables'
Clinton writes that she handed Trump a "political gift" in September when she told an audience of supporters that "you could put half of Trump's supporters into what I call the basket of deplorables."
Her admission of a mistake isn't without equivocation, though.
Clinton writes that she was "talking about well-documented reality," citing a 2016 study by the General Social Survey that found 55% of white Republicans "believed that blacks are generally poorer than whites 'because most just don't have the motivation or willpower to pull themselves up and out of poverty.'"
"Generalizing about a broad group of people is almost always unwise. And I regret handing Trump a political gift with my deplorables comments," Clinton writes. "I know that a lot of well-intentioned people were insulted because they misunderstood me to be criticizing all Trump voters. I'm sorry about that."