When a book is published “out of series”, it means that it does not fit into the publisher’s normal series numbering. This can happen for a number of reasons. For example, the book might be a spin-off from the main series, or it might be a prequel or sequel to the series.
There are a few different ways that a book can be published out of series. The most common is for an author to write a book that is not part of a series, and then later decide to turn it into a series. In this case, the book is published as a stand-alone, and then later books in the series are published. This can happen when an author writes a book that is popular, but does not initially plan to turn it into a series.
Finally, a book can be published out of series if an author writes a book that is part of a series, but the series is later cancelled. In this case, the book is published as a stand-alone because there is no longer a series for it to be part of.
There are a few different reasons why an author or publisher might decide to publish a book out of series. One reason is that the book does not fit the series’ continuity. This can happen if the book is set in a different time period than the rest of the series, or if it has a different tone or genre. Another reason is that the author or publisher feels that the book will be more successful as a stand-alone than as part of a series.
Out-of-series books are an important part of the publishing industry because they provide readers with a greater variety of books to choose from. They also allow authors to experiment with new genres or topics, which can lead to more successful and popular books.