This is the age-old question, and the simple answer is that you know your child best. My eldest was not ready for Harry Potter in second grade, even if we read it together. He frightened easily, and I knew it wasn't for him. That being said, some of his friends began reading it with their grownups even younger! Pay attention to your child's particular sensitivities when making the decision as to when to begin this series. Remember that when the series begins, Harry is only eleven years old. As the books progress and Harry and his friends get older, the books become more complex and darker as well.