I've just done something I've been planning for a while, though in the end it wasn't as easy to do as I thought it would be. I donated the first half of my SF book collection to the local library. As soon as I can pack and transport the second half, it too will be given away.
These books were the focus of my life for many of my teenage years (probably too much the focus). Needless to say, I read them all; most of them more than once and many of them numerous times.
The collection stopped being updated by around 1990. It included all of Larry Niven's works up to that point. All of Isaac Asimov's SF books. Many books by Robert A Heinlein. And hundreds of other SF (and a few fantasy) books as well.
I considered trying to sell them, though it seems that the amount of work involved to get a significant sum of money would be too great.
And actually I like the idea of the books being available at the local Modiin public library. I hope that many people find them and enjoy them as I had.