1. What will the libraries intend to do?
2. They buy same 10 books per library if the book is the best seller.
3. After "flavor expiration date" (after it lost its popularity).
The libraries don't want to keep "the best seller" books after it lost its popularity because they consider it is a wast of space.
So they will give them out by lottery to the people.
確かにいい分はあるだろう。They may have valid reason to do that (to give away the books)
But the writer wonders whether it is an ideal service (for the book lovers).