iBooks Author: Auto-saved files may be larger than expected

Some users may notice their iBooks Author (.iba) files are larger than expected in OS X Lion v10.7.4 and earlier due to the way Lion's autosave feature stores information about previous versions of the file.

Update to the latest version of OS X.

After updating your software, your existing iBooks Author files won't decrease in space, but additional revisions and new files won't experience the same issues with file size. If you're low on disk space, you can reclaim some of this space by duplicating your iBooks Author file in the Finder, and then deleting the original. Previous version information for this file will be removed, and the new version will use less disk space.

Note: This won't affect version information used by iBooks Author when publishing or exporting your book.