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

Working in PowerShell (.Net regex) one of my favorite tools is https://ultrapico.com/expresso.htm. It does require registering for a free license but it's well worth it. Source: about 2 years ago

Then you need this or something like it: https://ultrapico.com/expresso.htm. Source: over 2 years ago