Ever since macOS changed how it syncs with iPadOS I have found operations unsatisfactory and I wonder if there is any solution.
I have a number of books which I read in Books on the iMac 10.15.3, although I mainly use this to sync files to my iPad 13.5. My sync is setup to sync selected books - I am reluctant to change this, because it threatens to delete all my books if I change the preference.
I regularly use AirDrop to upload files to the iPad (usually monthly reports and similar), which is certainly more convenient and faster than the process of old.
HOWEVER whenever I sync the iPad ALL the likes I have added by AirDrop disappear!
I have another issue - I put a number (60) of pdf into a Category on Books on the iMac, but when I upload to iPad there is no corresponding Category.