Novel series

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.

Reprint series of public domain fiction (and sometimes nonfiction) books appeared as early as the 18th century, with the series Poets of Great Britain Complete from Chaucer to Churchill (founded by British publisher John Bell in 1777). Later British reprint series were to include the Routledge's Railway Library (George Routledge, 1848–99), the Oxford World's Classics (Oxford University Press, 1901- ), the Everyman's Library (J. M. Dent, 1906- ), the Penguin Classics (Penguin Books, 1945- ) and the Penguin English Library (1963- ).

Reprint series were also published in the United States, including the Modern Library (Boni & Liveright, 1917- ), in Germany, including the Universal-Bibliothek (Reclam, 1867- ), and in most other countries of the world.

In 1841 the German Tauchnitz publishing firm launched the Collection of British and American Authors, a reprint series of inexpensive paperbound editions of both public domain and copyrighted fiction and nonfiction works. This book series was unique for paying living authors of the works published even though copyright protection did not exist between nations in the 19th century.

Fictional series typically share a common setting, story arc, set of characters or timeline. They are common in genre fiction, particularly crime fiction, men's adventure and science fiction, as well as in children's literature.

...
Wikipedia