I would imagine past highscool, or the last education level with mandatory book reading, book reading falls off a cliff. And ever for mandatory book reading,I guess about half of students just read some kind of notes instead of the actual book.
To be fair a lot of students don't bother to read books school assigns as textsx because the way schools run things actually reading, engaging, and thinking about it is a disadvantage. There are certain themes and points your teachers want you to mention in your answers and any analysis outside of that will be considered "incorrect" or given lower marks, even if they relate to the text and the theme being studied.