Book crossing: not as new an idea as I thought

They do say there's nothing new under the sun, and one of these days I'll stop being surprised when it turns out true again. Book crossing is something I've heard of fairly recently, essentially it's leaving books lying around and hoping some delighted new reader will happen upon them (there's a bit more to it than that when tracking etc comes in, but that's the basic idea). So it was interesting to read, in The Intellectual Life of the British Working Classes by Jonathan Rose (a fascinating book, of which no doubt much more anon), that in the early nineteenth century shepherds in the Cheviot Hills regularly left books they'd finished with in nooks in boundary walls for other shepherds to find, read and pass on in turn. If it was happening there, it probably happened elsewhere too. I now have an urge to write a story about the life-changing discovery of a book tucked in a wall on a bleak hillside - it's a truly inspirational thought.