There is some debate on what constitutes children's literature. Most broadly, the term applies to books that are actually selected and read by children. Conversely, the term is often restricted to books various authorities determine are "appropriate" for children, such as teachers, professional reviewers, literary scholars, parents, publishers, librarians, bookstore personnel, and the various book-award committees. Anderson defines children's literature as all books written for children, "excluding works such as comic books, joke books, cartoon books, and nonfiction works that are not intended to be read from front to back, such as dictionaries, encyclopedias, and other reference material".
In addition to genres--such as traditional literature, fiction, fantasy, biography, informational, and poetry--books can also be categorized by their various formats, such as picture books, easy-to-read books, illustrated books, chapter books, hardcover books, paperback books, grocery store books, and series books. There is considerable controversy on whether grocery store (particularly merchandise) books are considered literature. Included in this debate are comic books and graphic novels.
While most children's literature is specifically written for children, many classic books that were originally intended for adults are now commonly thought of as works for children, including Mark Twain's Adventures of Huckleberry Finn. Conversely, some works of fiction originally written or marketed for children are also read and enjoyed by adults, such as Phillip Pullman's The Amber Spyglass, and Mark Haddon's The Curious Incident of the Dog in the Night-time, both of which received the Whitbread Award, which is typically awarded to adult novels. Also included are the works of J. K. Rowling and Shel Silverstein. Additionally, the Nobel Prize for literature has also been given to authors who made great contributions to children's literature, such as Selma Lagerlöf and Isaac Bashevis Singer. Often no consensus is reached whether a given work is best categorized as adult or children's literature, and many books are marketed for both adults and children/young adults.
There are a number of problems inherent in defining a class of books as "children's literature": For example, much of what is commonly regarded as "classic" children's literature speaks on multiple levels, and as such is able to be enjoyed by both adults and children. For example, many people will reread Alice's Adventures in Wonderland or The Wind in the Willows as adults and appreciate aspects of each that they failed to notice when they read the books as children. Many critics regard such multiplicity as having drawbacks, however; an adult may see the darker themes of a book and deem it unsuitable for children, despite the fact that such themes will likely be lost on younger readers.
One example of this is Mark Twain's Huckleberry Finn, throughout which the word "nigger" is used liberally. Many people feel that the word's racist and discriminatory connotations make it unacceptable to use anywhere, and particularly in a book aimed at children. Others, however, claim that to call the book racist because of this usage is to miss its point; Huckleberry Finn shows an admirable black character who becomes the voice of reason for a cast-off urchin and a middle-class white boy. Peter Hollindale, the educator and literary critic, applauded the book as "one of the greatest anti-racist texts of all time" and T. S. Eliot called it a "masterpiece".
Anderson suggests that literary elements should be found throughout all of children's literature. These important elements include characters, point of view, setting, plot, theme, style, and tone.
Anderson also suggests that every teacher should have at least 300 books in their classroom library.Anderson states that there are "several common themes in traditional literature" they follow along the lines of "Triumph of good over evil, trickery, hero's quest, reversal of fortune, and small outwitting the big," "Because one of the purposesof folklore was to transmit cultural values and beliefs, the theme is uaually quite apparent."