Almost 3000 open-content textbooks that anyone can edit. "Wikibooks is for textbooks, annotated texts, instructional guides, and manuals. These materials can be used in a traditional classroom, an accredited or respected institution, a home-school environment, as part of a Wikiversity course, or for self-learning. As a general rule, only instructional books are suitable for inclusion. Non-fictional books (as well as fictional ones) that aren't instructional aren't allowed on Wikibooks. Literary elements, such as allegory or fables, that are used as instructional tools can be permitted in some situations."