The MediaWiki software automatically recognizes inline ISBNs. For example, the wikitext
ISBN 0-12-345678-9 becomes ISBN 0-12-345678-9 (the dashes are optional), which corresponds to Special:Booksources/isbn=0123456789. This creates a link to a special page on book sources, where readers can obtain more information about obtaining a copy of that particular book.
This function may be useful in helping users to determine which books were used as references for a specific article, because it provides links to various online bookstores. However, ISBNs only identify a specific edition of a book, and the reader will not see the full range of the versions of the book for sale. Therefore, do not use ISBNs alone as a means of identifying books; add a full and proper citation in addition to the ISBN. (See cite your sources for more information about proper citations.)
To discuss additions to the book sources page, please see Memory Alpha talk: Book sources.