How to manage my books in iCloud

In the past, I could manage my books in iCloud by going to System preferences -> My account -> iCloud -> Manage. Then I could select Apple Books and show the contents as a finder folder. That allowed me to look for the largest books and be able to transfer them to my local Hard drive. But since a few months, when I do that I get an error message when I click on Apple Books, stating that "an error occurred during loading of the detailed presentation. Try later again".