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Here I am with a load of books which are no longer useful to anyone except very tiny niche collectors, so by handing them off to a library I'm essentially saying to a bunch of dedicated librarians "destroy these books for me so I don't have to destroy them myself." I don't want that kind of guilt, so I was thinking of recycling instead.

Don't do their thinking for them. Libraries are in contact with many more niche collectors than you. Be wise and take them to a library, where there is a possibility that some scholar who is researching the "Social Trends in Early 1990s Computer Instruction Manuals" can find them.

He can't find it in the already-shredded bin of your local recycling outlet. Leave guilt behind and take up simple wisdom. Give your books to the library. They might see a diamond where you see a pile of coal.

I knew a man who was director of a university library system for years. He gained a degree by walking around the English countryside studying old chimneys, insightful remnants of a previous era where everyone else saw a pile of rocks where a house had burned down. He got a degree out of it, and is to this day an amiable chap with fine stories of the English countryside.

I personally am always looking for 1960s-era computer books which most other people consider to be worthless.

Get them to a library.

-Jared