Petition Age Appropriate Reading for Children

All books should have an age 'guideline' on them so that children and parents at a glance can tell if the content of the book is appropriate, just as we have on films. My step daughter at 12 yrs of age recently read the book 'Cry silent tears' which is a true story of a boy seeing his father burn to death and who was later raped and very badly abused by family members. The detail in the book was not appropriate for a 12 year old but unfortunately we did not realise until too late. I fully understand that children should be encouraged to read books and that different children have varied abilities but this is only a guideline and if we have this on films why not on books! We need to protect our children and this would be one easy quick way to tell if our child is reading a book that may not be suitable for them.