The shopping bag dumped on the library desk, the startled librarian: "Some of these books look like they've never been used."
I nod sagely, "Reference books. Tell me, do you actually want technical stuff like 'Routing in the Internet'?"
Yes, apparently. They can be sent to a bigger library such as Bridgewater (sic).
I intend to donate the bigger portion of my telecom books. It's not altruism - I know this stuff and it dates so fast that an Internet refresher is the only way to get current.
I value the newly-empty shelf-space and have a, possibly naive, vision of some earnest eighteen-year-old studying BGP intently from my donation and henceforth devoting their life to network engineering - to the greater good of humanity.