What a fantastic idea. I've been in the habit of leaving books behind for years and wondering what happened to them. I've left then on planes and boats and planes. I've finished them in restaurants, hotels, and park benches and left them behind. Haven't
left one in a bar....yet. When a friend told me about bookcrossing.com, I was greatly surprised.
I travel extensively. As I write this, I'm in Istanbul, Turkey (of course), and I've already left two books. One in the Istanbul airport and one in the hotel where I'm staying (Movenpick). I usually travel with inexpensive books that are light reading to leave behind. It makes room for the treasures I acquire from around the globe. Some books I simply cannot part with. To paraphrase: "They'll get my books when they pry them from my cold, dead hands."
If you find one of mine. Enjoy!