What to do with 20 year old technical books?

The market here in OZ has segmented into five

1) people who come, pick out the eyes, underpay you and you still have to destroy the rest via the dump.

2) people who come, underpay you and take the lot to pick out the eyes.

3) charities who come, don't pay you anything, and you lose the problem.

4) shops who will, grudgingly, underpay you if you pick out what you think are the eyes, and bring them in.

5) customers who will whine at you directly on Amazon, Ebay, or Gumtree or Craigslist, if you sell direct, at what you think is a fair price, completely under costing your own time, effort, postage, unpaid, hijacked and lost sells. PS your tax status on this is moot. But, you can incur costs which exceed your profit. Plus, when do you pull the plug?

I've done, or had done to me, all of these. (partner ran a s/h bookshop in the early 90s, we had thousands of books before we downsized, we donated to flood victims and ultimately lifeline who do an annual university sale, but we kept back a box of 1st editions of some things for future risk-sell)

Tech books are almost universally worth less than you wish. They age out rapidly except for a very very very small cohort. If you can scan ISBN barcodes and write python you can probably find these from some simple scripting. Or, pay some intermediary who has written this as a product, and will become rich on $$$ from you, while you find the books are worth less than the $$$ you paid for the software.

At one point, I had a decade's worth of SANS course material. So much of it was ancient and no longer valid. I threw it away. It wastes space and could only lead others astray since the industry is always progressing, and Windows NT bugs and hardening guidelines are pretty much meaningless today. Ironically some of the tools SANS taught decades ago are still pertinent today, but courses on them alone... not so much.

There are some that I really enjoy and I keep them. But they are very much the minority. Outdated stuff goes to the trash, because when it comes to collectables, most technical books are not and never will be. The ones that are, really are.

I still have original QNX manuals because although I'll probably never use a QNX system in a technical manner ever again, there are things in those manuals that are pure gold. Ironically, some of the material is considered modern because of SBCs and whatnot. Like Photon, which under a different umbrella, entails a fairly common feature set these days. So I keep them.

A bunch of 15 year old PERL books? Trash. Not the PERL 5 stuff, but that's because I'm not the least bit interested in PERL 6, so there's no update of the bookshelves there. But I definitely haven't kept the pre-Perl 5 books. Why would I? Same with all the old Linux Administrator's Guides et al, because nothing they recommend and focus on even exists in that format anymore.

I know how you feel but the best thing to do is to recycle them. I had a bunch of them --10 years old plus. I tried to sell them, donate them or give them away to people I thought might be interested in them. No luck, they have no value.

You have a truck load full of books so bite the bullet and hire someone to take them away.

Are you in the US? Donate them to a library and take it off your taxes.

Donate to a library or museum? Recycle otherwise would probably be your best options