One of the most depressing things I had to do when my mother died and we cleared out her house was disposing of my Dad's books. There were hundreds. Colour photo non-fiction, modern fiction, paperback novels, hardback classics etc were pretty easy. The family took as many as we had space for. But there were masses of complete collections of old (pre-1950's) non-fiction works, like a full set of 1930's Swedenborg. Absolutely no one wanted them. We contacted every book dealer we could find. We offered to give them away but no takers. Charity shops wouldn't touch anything old, regardless of condition. They said they didn't have the space and they'd never sell.
In the end, one day before we had to hand the keys to the house buyer, myself and the new owner took two car loads of immaculate old books to Blandford tip. There was nothing else we could do. We told the lads at the tip to help themselves and save anything they could and they did dive in and pulled a lot out and set them aside, and we invited the public there to take whatever they wanted but we stilled filled one large industrial sized recycling wheelie bin with perfectly good books, many that will probably never be in print again. It was one of the most horrible things I've ever had to do. I felt like a book-burning Nazi.