[Elhem Enohpi]

Thanks for the replies. I'm specifically looking for how to sync bookmarks, highlights, reading position, etc. without uploading my books to iCloud Drive. I've transferred the books from the computer to the phone with a cable. I don't want the books themselves in iCloud Drive. This worked fine on older iOS, but doesn't seem to work anymore.

I think you just need to have iCloud option for Books turned on. ... If you also want book to upload to iCloud Drive then turn on iCloud option for Books settings.

I don't want it to upload to iCloud Drive. But there is no other iCloud setting on the phone that I can see. There used to be "Sync Bookmarks and Notes" and "Sync Collections", which would work without iCloud Drive. But those are gone now. The instructions:

Go to Settings > [your name] > iCloud, then turn on both iCloud Drive and Books.

result in the books getting uploaded to iCloud Drive, which I don't want.

Works for me. I have iMac, iPad Pro, iPad mini and iPhone all syncing perfectly via iCloud Drive.

But you have your books uploaded to iCloud Drive, right? That's what I'm trying to avoid. I just want to transfer the books with a cable, not upload them to iCloud Drive. I don't want to use up the space in iCloud, I want to be able to put only select books on the phone and not my whole library, and also I have a different Apple ID for Books (the one I use for purchases) than the one I use for iCloud.

I want to continue to use the old way of syncing, before Books in iCloud Drive was a thing. That's how I've always done it, and it still works between two Macs, one on Monterey and one still on Mojave. So is it really the case that it's no longer possible with iOS, and you're now forced to use iCloud Drive?