In AirWatch Console 7.3 and 8.0, administrators using a non-US locale for their account are unable to upload some internal books due to a formatting issue with the "Released on" date. The Console will incorrectly parse dates in the mm/dd/yy format.
By changing the locale of an administrator (Accounts -> Manage Account Settings -> Locale) to US, iBooks can be uploaded successfully.
This issue has been given identifier FCA-177486. This issue has been resolved with AirWatch 8.0 FP9.