Delivering all over the country, Pen And Parchment has got titles starting at INR 49 (although the in-demand ones might cost a little more). They’ve got classics, fiction, adventure, mystery, non-fiction—the works. Make some space in your bookshelf and raid this site, we say. They even do occasional sales on their social media, where they give out a list of books for a flat price like INR 99.
Note: Their website is currently closed. Until it's back up, you can follow them on Facebook.