According to the changelog, iBooks Author offers a new ebook template and new options for linking inside an ebook. There is also mention of improvements to widget behaviors, including an option for autoplaying the media and keynote widgets (that would count as a dis-improvement, IMO).
And last but not least, Apple has also added an option for importing Epub files made elsewhere and InDesign files. An early report suggests that this feature creates a mess when IDML files are imported, but on the plus side iBooks Author does try to retain the formatting during the import process.
You can find the app in iTunes.
What’s New in Version 2.2
• Import ePub files
• Import Adobe InDesign IDML files
• Create customized books with new Blank templates
• New hyperlink options: link to a location in another book, link from an image, and more
• Improved transition support in Keynote widget
• Enable auto-play for media widget, Keynote widget, and HTML widget
• Readers can now interact with the HTML widget right on a book page