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. Publishers' reprint series Reprint series of public domain fiction (and sometimes nonfiction) books appeared as early as the 18th century, with the series The Poets of Great Britain Complete from Chaucer to Churchill (founded by British publisher John Bell in 1777). 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. Later British reprint series were to include the Routledge's Railway Library (George Routledge, 1848–99), the Oxford World's Classics (Oxford University Press, from 1901), the Everyman's Library (J. M. Dent, from 1906), the Penguin Classics (Penguin Books, from 1945) and the Penguin English Library (from 1963). Reprint series were also published in the United States, including the Modern Library (Boni & Liveright, from 1917), in Germany, including the Universal-Bibliothek (Reclam, from 1867), and in most other countries of the world. Fiction books A novel sequence is a set or series of novels which share common themes, characters, or settings, but where each novel has its own title and free-standing storyline, and can thus be read independently or out of sequence. A novel sequence contains story arcs or themes that cross over several books, rather than simply sharing one or more characters. Fictional series typically share a common setting, story arc, set of characters or timeline. They are common in genre fiction, particularly crime fiction, adventure fiction, and speculative fiction, as well as in children's literature. Some works in a series can stand alone—they can be read in any order, as each book makes few, if any, reference to past events, and the characters seldom, if ever, change. Many of these series books may be published in a numbered series. Examples of such series are works like The Hardy Boys, Nancy Drew, and Nick Carter. Some series do have their characters go through changes, and make references to past events. Typically such series are published in the order of