Maybe instead of a book, a supermarket checkout tabloid would have been more appropriate. 

The author of the explosive new Trump book says he can't be sure if parts of it are true

"...But the book's author, Michael Wolff, says he can't be sure that all of it is true.

The author of the explosive new book about Donald Trump's presidency acknowledged in an author's note that he wasn't certain all of its content was true.

Michael Wolff, the author of "Fire and Fury: Inside the Trump White House," included a note at the start that casts significant doubt on the reliability of the specifics contained in the rest of its pages. ...."

http://www.businessinsider.com/michael-wolff-note-says-he-doesnt-know-if-trump-book-is-all-true-2018-1