I have the same question.
1) I have searched through the iCloud drive on my Mac as well as on Safari. No books.
2) I have used iExplorer to open up previous backups of my iOS devices. Also no books.
3) I have looked through the iBooks folder in my MacBook and the books that are found in this location are those that have been purchased from iBooks store:
~/Library/Containers/com.apple.BKAgentService/Data/Documents/iBooks
I do have a copy of all the epubs and pdfs that I created and uploaded into iBooks. The problem is that one of the saved copies is corrupted (don't know when and how) so I now need to retrieve the working copy from iBooks. The corrupted book is in epub format and it's working fine in my iPhone and iPad. This working copy must be somewhere in iCloud.
It's easy to retrieve a copy of a pdf from iBooks. I open the pdf in iBooks, then mail a copy of it to myself. So it's easy to replace any corrupted copies of saved pdfs that I have uploaded into iBooks.
But there is no such mailing option for epubs! When you try to do that, iBooks will only paste a description of the book into the email which basically says "check out this book". I can understand why you shouldn't be able to email yourself a copy of the epub if it's DRM (like those purchased from iBooks store).
And for those that are not DRM (like those you created on your own), there is either no option to email a copy, or when there is an option, the email opens up to an error:
pingsfailureType5002customerMessageAn unknown error has occurredm-allowed
Where is the working copy of my epub?? It must be somewhere out there since I can read it in iBooks, but where?? And how do I get back a copy of it??
