I think there are just as many who refuse to believe anything in the book is not true. (Just because it is in print, does not mean it is correct.)
But then too many people don't know and/or follow genealogical standards. If facts/statements have no sources, you need to research and find sources to prove those facts/statements as correct or incorrect. Blindly accepting undocumented facts/statements can lead one down the wrong path and possibly researching the wrong family.
I also discovered the other night that the book didn't get a good start ... an initial review lamented that he made up his own numbering system rather than use one of the various standard numbering systems at the time.