In children’s literature, the major categories of books are:
Picture books: (ages birth–5) These are the earliest books read to children, featuring illustrations on every page and fairly short sections of text.
Easy readers: (ages 4–7) When children are ready to begin reading independently, they usually start with easy readers, which are books with simple vocabulary, simple sentence structure, and basic story arcs.
Middle-grade: (ages 8–13) Middle-grade books are written for children who have mastered the basics of reading and are ready to take flight in books with more complex characters, stories, and themes. Within the middle-grade category, books may be further separated into lower middle-grade and upper middle-grade, based on the length and complexity of the book.
Young adult: (12 and up) Young adult books are usually longer than middle-grade books, have adolescent characters, and typically have more mature themes.