I was directed to this website today, and I've got to admit I'm a little enchanted. The idea is you register a book, and then give it away or trade it or sell it or leave it somewhere, with a number in it and a note, and you write a journal thing about it, so that future reader/finders also go online and write about it, and you can see what happens to your book and all experience the joy of reading together with strangers. It seems rahter romantic. In much the way the whole marginalia thing captures my imagination, which I posted about a while ago.
And it wouldn't take much to make a very sentimental movie about the idea. Unless it was some horribly unromantic book. "I knew we would fall in love when I found her name in my used copy of 'a modest proposal', complete with underlining."