There are some disadvantages of too much reading. For instance, when people spend a lot of time reading books, they eyesight will become myopic, which is another word nearsightedness. Second, people who spend a lot of time reading books will cause them more likely to be antisocial, which is one of the biggest issues for some people. Last, I would think too much reading will cause behavioral and mental problem, which cause some people to easily forget things and don't really care about what's going on in their surroundings.