I purchased a book a while back that had a version update. When I tried to update it, it wouldn't update. Since, I've updated my iPad, logged on and off from my iCloud account, did the same with my App Store account, deleted and reinstalled iBooks, but the book still doesn't appear in my library. Under the purchased tab, my book simply appears as "Downloading". The tab is grayed out, and tapping it doens't do anything.
Note: I've deleted and re-downloaded my other books with no problem. This book that won't appear, won't even display its icon - accompanied by the little icloud corner tab - within my library.