Main different between Book Librar y Pro and Shop version - in Book library shop version you may sales all books not only through Amazon affiliate, You may sell all with help local shop built on Virtue mart
Also in Shop version - you may gathering all books to cart and buy all from amazon at one click
i could charge a fee to the user that works with my service for selling your books.
There are need more details, how you wish that need work, but possible different variants. Also you may check ours componenr Simple Member ship - ordasoft.com/simple-membership.html,
Pro version - permit for you create payment membership site.