To submit a version number, include the following prefix attribute in the <package> element in the OPF file:
<package xmlns="http://www.idpf.org/2007/opf" unique-identifier="bookid" version="3.0" prefix="ibooks: http://vocabulary.itunes.apple.com/rdf/ibooks/vocabulary-extensions-1.0/"> Note: In the prefix example above, the space between ibooks: and http:// is important; it needs to be a single, regular space character and not a return, non-breaking space, or any other kind of whitespace.
The version of your book is specified within a meta element in the package document. The meta element has a property value of "ibooks:version":
<meta property="ibooks:version">1.1</meta>In addition, you must supply some text explaining the changes made in the updated version using the <version_whats_new> tag in the metadata XML delivery. See Book Versioning Metadata XML File Annotated in the Apple Books Book Package Specification for details.
Note: If you create a new version of a book, keep in mind that the idrefs in the OPF should always refer to the same content across different versions of the book. For example, ID "html9" should refer to the same chapter in both versions of the book, even if the actual name of the HTML file or the order of the elements in the spine may have changed. By keeping the idrefs the same, the annotations a customer made in a chapter in one version of the book will remain with the correct chapter when synced to the newer version. If you do not keep the idrefs the same, the annotations end up in the wrong chapter in the new version.