Interestingly, the person getting the most blow back for this book is not Trump but Bannon. He has been forced to step down from his post at his not very legitimate news outlet.
Not super surprising. There's not a ton of really revelatory stuff about Trump in the book, but Bannon broke ranks - and, the powers-that-wanna-be can't have that.
At this point, regardless of how much truth there is in Trump's dementia or bottom buddy role with Putin, the Republicans have latched on to his sunken ship. The 33-37% of core Republicans will never, ever, ever, ever not support a Republican. They have to hold on to dear life at this point because Trump going down not only loses them the Senate and Congress but the Presidency. They have too much damage to inflict over the next few months before Mueller comes out with more indictments.