A book series is a sequence of books having certain characteristics in common that are formally identified together as a group. Book series can be organized in different ways, such as written by the same author, or marketed as a group by their publisher.

Publishing is the activity of making information, literature, music, software, and other content available to the public for sale or for free. Traditionally, the term refers to the creation and distribution of printed works, such as books, comic books, newspapers, and magazines. With the advent of digital information systems, the scope has expanded to include digital publishing such as ebooks, digital magazines, websites, social media, music, and video game publishing.