I'm using iBooks 1.7 on macOS Sierra (but have had this issue since iCloud syncing via iBooks has been available). Books added via file > Add To Library are not being synced across my devices.
I have an iPad and an iPhone using the same apple ID all supposedly syncing bookmarks, collections iBooks data etc and yet it's not actually syncing any of them.
The most progress that I can see is a cloud logo in the top right of the books on a (3rd or 4th) restart of iBooks and an uploads arrow listeninglisting the newly added books, but there's no option in the UI to start the uploads that are listed.
Has anyone had this trouble? I'm absolutely at a loss and it's a recurring issue.
Thanks SE!