Because children's books span such a wide age and reading-level range — infants to teenagers — there have to be distinct divisions that break them down into smaller categories. For example, a twelve-year-old may prefer reading about a thirteen- or fourteen-year old protagonist to one who is ten years old. In other respects, such as complexity of language, books about these two ages may be similar. This is one illustration of the fine line between middle grade and young adult. This chapter will outline the different types of children's books.