"HELP! HELP! WOLFF! WOLFF! WOLFF!"
Here is the relevant part of the note, from the 10th page of the book's prologue:
"Many of the accounts of what has happened in the Trump White House are in conflict with one another; many, in Trumpian fashion, are baldly untrue. These conflicts, and that looseness with the truth, if not with reality itself, are an elemental thread of the book.
"Sometimes I have let the players offer their versions, in turn allowing the reader to judge them. In other instances I have, through a consistency in the accounts and through sources I have come to trust, settled on a version of events I believe to be true."
The book itself, reviewed by Business Insider from a copy acquired prior to its Friday publication, is not always clear about what level of confidence the author has in any particular assertion.
Lengthy, private conversations are reported verbatim, as are difficult-to-ascertain details like what somebody was thinking or how the person felt.