It fixes the icon and the rights of the files (thanks to @bass63 for pointing this).
If you had previous version follow those steps :
- uninstall it with cydia (this uninstalls iBooks)
- install iBooks from the AppStore,
- reboot,
- install xBooks from Cydia,
DO NOT TRY TO LAUNCH iBooks before xBooks !!
As usual use this at your own risks.
Happy reading !