When reading fiction, visualization takes place automatically. Most people use it to follow the action in short stories or novels. It is much easier to follow the action with visualization when the author has used a familiar setting with familiar words. Even when some of the words are new, visualization keeps readers on track, and does not slow them down. When reading for pleasure, the primary goal is to enjoy the story.
Readers simply follow the author's line of thought to see what is going to happen next.
They can remember the story because they use visualization to follow the action. When reading a textbook, it is difficult to follow the abstract thought process using visualization because the student can not make visual images or follow the action if he doesn't know the subject. New words and terms will usually slow the student. This is common because textbooks are designed to teach new concepts and ideas. Reading speed increases when a student recognizes and understands the new words and terms.