Issue with organising books in the Books app on iPad and iMac

I am in the process of transferring all my e-books (mostly pub, a few pdf files) to the Books app. The app synchronizes between iPad, iPhone and iMac. Currently the app holds 300+ titles. The authors are listed {last name, first name}. When I sort the books by author, some books are sorted to first name, others are sorted on ?book title and some are sorted on last name.

If I sort manually on the iMac and later open the app on my iPad (7th gen), the order in which I put the books on the iMac can be changed on the iPad. Specifically, some of the imported books I sorted, will appear again top of the list.

Can anyone tell me if I am doing something wrong, or at least explain the behavior of the app to me in this respect?

Also, it seems that sorting manually, I can only sort 1 book at a time. Is there an easier way, as this is very time-consuming.

Thx