MacRumors is reporting that they have received word from a source that claims to know information about the un-released iTunes 9.1 update. According to reports, it will be released around the same time as the iPad this Saturday and its main new feature is eBook content to support the iPad.

According to the source, the existing "Audiobooks" entry in the iTunes Source list will be replaced with a broader "Books" section. A similar change will made to the sources for managing content on connected devices such as iPhones, iPods, and iPads. The revamped "Books" section for connected devices will reportedly display all book content compatible with a given device for easy content management.

The update is also going to reportedly improve Genius Mixes, the feature in iTunes that automatically selects songs "that go great together." Users will be able to have more control over Genius Mixes, including the ability to rename them and organize them. Also, users will reportedly be able to delete them by right-clicking.

Finally, the iTunes 9.1 update is reportedly going to bring changes to device support, rearranging the summary pane of the Sync screen and moving the "Check for Updates" and "Restore" buttons to the left side. Also, users will be able to have to choice to convert their songs to 128 kbps AAC format when syncing to them to the device.

There is no further information regarding iTunes 9.1 and no release date has been officially announced yet.