Michael Wolff wrote in its beginning pages of his new book, "Fire and Fury: Inside the Trump White House," that much of the information inside is based on sources that may not have been telling the truth.

"Sometimes I have let the players offer their versions, in turn allowing the reader to judge them," Wolff wrote. "In other instances, I have, through consistency in accounts and through sources I have come to trust, settled on a version of events I believe to be true."

Wolff has said in media interviews that he stands by his reporting, but the author's note acknowledges that he was merely piecing together the information he gathered as it came from his sources, regardless of whether he could confirm their accounts.

"At the same time, it is worth noting some of the journalistic conundrums that I faced when dealing with the Trump administration, many of them the result of the White House's absence of official procedures and the lack of experience of its principals," he wrote. "These challenges have included dealing with off-the-record or deep-background material that was later casually put on the record... In the end, what I witnessed, and what this book is about, is a group of people who have struggled, each in their own way, to come to terms with the meaning of working for Donald Trump."

The controversial book attempts to look at Trump's early presidency and repeatedly suggests that Trump is unequipped mentally and temperamentally for the White House.