That's left up to your discretion as a parent. The important thing to remember is that these novels contain powerful messages that will impact kids in a positive way, not leave them feeling sad and upset. While some novels (such as El Deafo) do have illustrations that are a bit strong for kids under the age of ten, we feel that the message they convey far outweighs that. It's a good way to introduce these things to children and encourage positivity and acceptance rather than tiptoe around them until the topic eventually comes up on its own.