High Quality Content by WIKIPEDIA articles! Children`s literature is for readers and listeners up to about age twelve; it is often defined in four different ways: books written by children, books written for children, books chosen by children, or books chosen for children. It is often illustrated. The term is used in senses which sometimes exclude young-adult fiction, comic books, or other genres. Books specifically for children existed by the 17th century. Before this time period it is generally believed that books were written mainly for adults. Additionally, most printed works were hard to come by due to their cost and were mostly available for purchase only by upper class society. Scholarship on children`s literature includes professional organizations, dedicated publications, and university courses.