Yes but,
First of all, I am not an O'Reilly fan and I don't have a strong inclination to read his book.
If I were so inclined, I would read the book with with a critical eye to it's content and whether O'Reilly's omissions make the book unimportant.
I think I would also like to compare it to a book on Reagan that does include the emotional opinions.
The problem with the latter is the author often has emotional opinions of his own and they sometimes show through in his work. Those who feel one way will love the book and those who feel the other way will hate it.
In the end it is all on the writer.
P.S. I guess it has to do with proximity, but it hard for me to believe that he could filter out everyone who had "skin in the game" for Reagan.