What Happened: Hillary Clinton's upcoming book on 2016 presidential election defeat

New York : Former Democratic presidential nominee Hillary Clinton would soon release a book titled "What Happened" in which she would opens up on her stunning 2016 election defeat to her Republican rival Donald Trump.

The book, to be published by Simon & Schuster in September, would explain how the former secretary of state came up short again in her fight for the White House, Xinhua news agency reported.

"Writing 'What Happened' was hard, so is what we see every day. As we move forward & fight back, I hope this helps," Clinton posted on her Twitter account on Thursday with a link to the book's page at amazon.com.

"In the past, for reasons I try to explain, I've often felt I had to be careful in public, like I was up on a wire without a net. Now I'm letting my guard down," Clinton wrote in the introduction of "What Happened".

"This is her most personal memoir yet," said Simon & Schuster on its Web page for the book in which for the first time Clinton reveals "what she was thinking and feeling during one of the most controversial and unpredictable presidential elections in history."

"Now free from the constraints of running, Hillary takes you inside the intense personal experience of becoming the first woman nominated for president by a major party in an election marked by rage, sexism, exhilarating highs and infuriating lows, stranger-than-fiction twists, Russian interference, and an opponent who broke all the rules," the publisher said.

The book describes "what it was like to run against Donald Trump, the mistakes she made, how she has coped with a shocking and devastating loss, and how she found the strength to pick herself back up afterward," it added.