A lot has been reported on it in news media. I wasn't going to buy it because I thought all the interesting stuff was probably already revealed.
But I did buy it and am about 1/4 through the 400 page book.
Definitely recommend it.
There may not be shocking new revelations, but the story does a great job of showing the inside story of the campaign from 2014 or so through the election.
The authors did interviews with dozens of key campaign participants throughout the campaign. The authors thought they were writing a book about how Clinton would win. But the ending of course had a final surprise.