Sometimes you see bookshelves in local busses here in Hamburg. You can bring a book you’ve already read, take another book from the shelf and when you’ve read the book you can swap again. I like this idea!
A few weeks ago a book swap corner opened at Helsinki-Vantaa airport. When you bring a book to the book swap you can put a sticker in the book to mark with whom and where the book has been travelling. That makes the idea of book swap even more interesting!