
I for example, am a big fan of the book "Waves & Beaches" by Willard Bascom, a long out-of-print book on the physics, dynamics of the ocean (and the spirit of longing to understand the nature of the sea), but which always only could be found for >$30 on Ebay or something like that.
I finally bought a copy (out of nostalgia) and actually enjoyed it again so much, I went to the trouble of sawing off the spine, scanning it and OCRing it to produce an eBook and prolong its life. For myself.
I have been tempted to share it, but have no idea how. But I imagine there's tons of books and people like this.