Ignoring your extremely bazaar fantasy that reporters record off the record interviews (other than as notes), the substance of Wolff's book in regard to the "President's" mental health and fitness for office is on the public record.
His tweets are public record.
His attempt to claim the the voice on the Billy Bush "grab them by the pussy" tape was not him and that is was digitally altered is on the public record.
His claim the Obama bugged Trump Tower is on the public record.
His claims about the crowd size at his inauguration is on the public record.
His speech the day after his inauguration to the CIA is on the public record.
I'm surprised that you are admitting that Michael Wolff's book is based upon previous publicly made statements instead of any interviews that Wolff pretended to make.
By the way.. you misstated what Trump said about Obama.. you said "Obama bugged Trump". What Trump actually said was "Obama WIRETAPPED Trump Tower" - which we now know to be true. Bugging is one specific thing.. wiretapping involves any form of intercepting communications illicitly. The definition of wiretapping expanded after the internet became a method of communication. Now wiretapping includes both audio AND electronic surveillance.
The crowd size comment was a rebound over the photos showing huge empty spaces - which were extremely misleading. What Trump should have said was that the crowds were normal, not small. Instead he said the crowds were huge, not small - which got him in trouble. Also, it was raining.. which people tend to forget. I recall watching video of villiage idiot George W Bush trying to put on a rain parka and failing - as Dick Cheney looked on in disbelief and laughter.
His Billy Bush comments were taken out of context. But then again.. so what?
Despite it's massive expectations, that "Fire and Fury" book has turned out to be a nothing dud.