Create and give age rating system for books, like films, that are mandatory and enforced by the Government. This could stop the wrong books getting into the hands of children.
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Parents often buy books for their children, sometimes from charity shops. I find it absolutely horrifying that some books read by young people contain very detailed, graphic and sexual descriptions which I believe is too inappropriate for any young person to be reading. In certain circumstances, there is nothing on the cover which gives any warning of this type of content.