To the people of today, if something is written in a book then it means that a significant number of people share the same view. This alone qualifies it in their mind as a valid, viable consensual reality. Reality is thus created by numbers, and numbers become God.
If you question their assumptions they will argue "do you seriously think so many good and intelligent people can be wrong?".
This is exactly the case in religion, where, rather than seeking truth through reason, people place their faith in what is popular and "viable". Or rather, they consider it reasonable to place their faith in numbers.