"Book" represents the abstract notion of a particular book, rather than a particular edition.  It is on this level that articles or discussion about a book should generally occur (e.g., the article about Mary Shelley's "Frankenstein" is on the book topic, rather than on one or more of the hundreds of editions it has gone through).  The book topic should also be used for connections to other types, such as films that have been adapted from a book.

Please see Entering Data for a Book for more information.