It's a pretty fair critique, but for me the good in the book still far outweighs the bad. With such an immense project and with so much information to cover, I fully expect there will be the occasional factual error or instances where the author draws a conclusion or makes an assumption that isn't totally accurate.
Ultimately, as much as I may love it, we're talking about the making of a TV show
here. It's not a history of the Civil War or the Lincoln presidency or anything.