>>24510819it depends
>18th century and beforeGenerally anything 18th century and before has some inherent value unless they're extremely mass produced pocket editions
>first editionsfirst editions in good condition are pretty much always worth something. but that only applies to popular authors though, a "newer" first edition finnegans wake will be worth more than a first edition 1830s book from an author nobody remembers
>illustrationsolder books with illustrations from famous illustrators like arthur rackham, nc wyeth, aubrey beardsley, etc in good condition are usually worth something, although modern reprints that use those illustrations aren't for obvious reasons
>controversial or edgy subject mattersex, drugs, the occult, from days when those subjects were more controversial are worth a lot
religious books generally aren't worth much unless they're very old (17th century and before) because people generally aren't religious days. Walter scott novels aren't worth much because he was extremely popular back then but isn't really popular now.