Have you heard of Pangobooks? It’s an app (and website) for selling books! Any book you have and want to sell can be listed. It’s super easy to buy and sell on this app/site.
You can create your own little book shop and list as many books as you want. I have sold quite a few books this way and have made some money. I also have bought from others and have had all good experiences.
Sometimes people will list their books super cheap too. Signed books, special editions from book boxes, and bookish items too!
Here is my account if this is something that interests you 🙂