A new tweak called Booksstand has just gone live in Cydia which allows users to put their iBooks inside the Newsstand folder on iOS 5 devices. The tweak actually lets you add shortcuts for your favorite books and PDFs in the Newsstand folder and access them directly in the iBooks app. Once the tweak is downloaded and installed from Cydia, users can export any iBook to the Newsstand by selecting it and using the ‘move’ option to put it in the Booksstand collection from inside the iBooks app (latest iBooks update required).
The tweak does not actually move any iBooks to a different collection but only makes them available in Newsstand. Once done, you can treat your iBooks like any other Newsstand applications.
You can download Booksstand for $0.99 from Cydia Store via BigBoss repo.