I’m going to go against the grain and say DO NOT give them to your library.
We get so many crappy books donated, and people are so proud that they’re helping the library, and preserving literacy, and you know what happens to old nonfiction in the three systems I’ve worked in? The Friends volunteers (mostly old people who shouldn’t be doing hard physical labor) have to take each one, cut the covers and spine off, and physically take the damn things to be recycled. All that takes up time they could be using with stuff that will actually sell, or (god forbid) be new enough for actual consideration on the library shelves. If you are hesitant, then call them, and be honest about the age and condition, and tell them you’re happy to recycle them yourself if they can’t be used by the library. Encourage them to tell you if they can’t use them AT the library, or if they are unlikely to sell or consign for much. (We are supposed to tell people we’re happy to take their donations even when we are crying inside about how worthless and time-consuming they will be for us.)
I can nearly 100% guarantee you that none of your nonfiction will be worth anywhere near the time and effort needed to check the prices on Amazon.
If you have a local bookstore that pays per book regardless of age (and you don’t mind them hating your guts for as long as they remember you), then take them there and be happy for the money. The bookstore will recycle or trash them as soon as you drive off.
If you need to feel you’re contributing to the community, give them to Goodwill or the Salvation Army, or save everyone a crucial step and recycle them your own self.