“Simply, Wikibooks is a collection of open-content textbooks.
Because the word textbook is open to interpretation, this document exists to help clarify which types of content are acceptable for Wikibooks. For example, The Complete Works of Shakespeare might be considered a textbook in an English Literature course, but such a text would be inappropriate for this site.
What Wikibooks includes
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.
Wikibooks includes both minor and major book-like projects.
Materials which may not be appropriate for Wikibooks should only be removed in accordance with the deletion policy.”*
*https://en.wikibooks.org/wiki/Wikibooks:What_is_Wikibooks