I need to buy a large amount of books, probably around 20-30k at least. Anyone knows of a book store with good discounts that I can buy from?

I have decided to build a library in my mom's village for the kids there. It would be in our native house there but accessible to everyone. I am planning to start with all the popular books for kids, so Feluda, Ghonada, Tenida books along with some English series like Sherlock Holmes, few of Enid Blyton's series and some scifi and fantasy staples.

Edit: Just to clarify, the library would still be a private thing for my family primarily. While it would be accessible to outside people, it won't be a public library. Its mostly for people in the neighborhood. But still pretty much a private collection.