This website is very similar to what I'm trying to create. Source: almost 3 years ago

Plugd | Founding Product Designer | Remote (US or Asia) | https://getplugd.com Plugd is like Reddit built for commerce, making community-generated content discoverable and shoppable. It's getting hard to find trustworthy content online, especially when it comes to products. But small, niche communities, like the ones on Reddit are one of the few places you can still find it. Plugd is solving this problem, while... - Source: Hacker News / about 3 years ago

My first stop is always bookfinder. Doesn't cross-reference every site but it does a good chunk of them. Source: 12 months ago

If an era (say civil war) go to http://bookfinder.com. Now on the front page click Advanced Search. You can select year of publication. So for civil war I would plug in up to 1900. Source: about 1 year ago

First you need to learn to grade the book, as value is related directly to condition. Then you can look the book up on bookfinder.com and see what it's worth. But... there's a caveat. There's lots of "script sellers" out there, sellers that don't actually own the book - but which scrape the data, markup the price and offer it for sale, planning to buy it when you do. There's also many utter idiots who will... Source: about 1 year ago

If you NEED to purchase a book, use bookfinder.com to find the cheapest books. Always verify the ISBN to make sure you get the correct one edition. Source: about 1 year ago

You should also check bookfinder.com. Source: about 1 year ago