There are people who thinks that teenagers should choose books by themselves. Other people are convinced that children must read the "correct" books, which are censored.
The first opinion looks like something totalitarian. Teenagers, and are not only they, must read books, which they are wanted to read. Because if you will read the bad book, by your opinion, you will not fully enjoy reading. Moreover, every person have different books which they are loved, because all people  have difference with their preferences.
As to another opinion, it is more democratic. When you read a good book, which you have chosen to yourself, you feel that exerything was done right. You can read books that suits you and you can improve yourself. For example, teenagers likes reading book,
 like "Harry Potter", because they really loved them and they can learn what is kind, friendship, brave, love e.t.c.
But i can not agree with both statement. I think,
if teenagers will also read books without censor, they can found something which not good for them. Children are usually do not look on age limit, so the chance that they will choose a book not for them is raised. On the other hand, if parents will watch for his children and control what they read, it will be useful for both sides. Children will read good books with their age-limit.
I believe that children should not be allowed to read all books that they like because some of them are dangerous for readers.