"I find your post very confusing. "
Is it my description of the issue, or that the issue exists at all?
There is a book I want to get rid of completely. I can delete a local copy, but then that title still appears, and beside it is the little icon of a cloud with down-pointing arrow next to it.
If you google it, it is a common question with no satisfactory answers, when it's for OS X 10.13 or later.
"Firstly Books don’t show at iCloud.com."
I guess not, since I didn't see it there in Safari browser window. I can only think that it must be an uncharacteristic Apple interface design flaw - using the same made-up term for unrelated concepts.
I thought perhaps I only assumed (erroneously) that the download icon had anything to do with iCloud, but (in my defence) the Help file says:
Items you purchased from the Book Store or Audiobook Store are still in iCloud, even if you remove them from your Mac. They appear in your library with an iCloud status icon 
. You can download purchased books and audiobooks again.
Hence my confusion.
"Secondly, you can only Hide purchases that were made for Apple purchases."
I beg to differ.
This one book came from Smashwords, years ago. I selected it and tried "Show in Book Store" and the result is "Item not available. The item you've requested is not currently available in the Canada store."
And yet, when I choose to "Hide iCloud Books", the title disappears, along with a dozen others that I don't want hidden.
I get similar results for them, which I believe came from gutenberg.org. In addition, these were downloaded to my Mac Mini (2007) , which never (as far as I know) made use of iCloud. I don't know how these titles made it over to the MackBook. I did not use Migration Assistant or anything.
" It sounds somewhere along the line you have enabled iCloud Drive for Books,"
If you mean System Preferences / Apple ID / iCloud / iCloud Drive - Options... , then it's unlikely, since I did not enable iCloud Drive until tonight, just to see what I might find there. I had to agree to "upgrade" to it. The "Books.app" was already checked by default, but as I said, iCloud Drive was not enabled before tonight.
I unchecked Book.app in iCloud Drive options, but the title is still persistent in the Books library, with a download/cloud icon.
"... and when you disable it your books are no longer showing (which is how it is meant to work)."
Again, iCloud Drive was not previously enabled in System Prefs / Apple ID. and they were/are still visible (if not hidden).
" I don’t understand why you can’t just delete non-Apple books from the Books app – option control delete."
I don't see why that should work.
It's not listed as one of the keyboard shortcuts in the "Keyboard shortcuts and gestures in Books on Mac" Help file. None of them refer to "delete" in any way. Maybe it works for deleting them from a Collection, but not from the Library list.
Are you using an earlier version of Books or iBooks?
The "Delete books or audiobooks from your Mac in Books" Help file does say this, however:
- In the Books app
on your Mac, click Library in the toolbar. - In your library, select the book or audiobook you want to delete, then press the Delete key.
If you’re using iCloud for Books and you delete a PDF, book, or audiobook that you imported, it’s deleted from iCloud and all of your devices where you use iCloud for Books.
That did not work either. It only triggers an Alert sound.
