Do you think that they will just completely understand and accept the information in that book? The truth of what that person reads will be in conflict with their existing set of beliefs. The ideas in that book will be in conflict with so much of what they already accept as true. The belief system in their mind will reject the ideas on the page as not true. To accept as true the material in that book would mean the collapse of so much of the structure of their belief system. This would be uncomfortable and in an effort to avoid that discomfort their mind would reject the new ideas even though they have greater clarity.