I was at a public library in Kansas over the weekend and they had a neat idea for adult summer reading. They create grab bags with two or three books of the same genre and patrons can just grab one on their way out the door. They had mystery, romance, historical fiction, Christian fiction, and some non-fiction in addition to many others. The books are just donated paperbacks and have no due date. And smarty pants that they are, they put that big ol’ basket of bags and a catchy display right in the hall between the children’s section and the exit.
Now, if they manage some sort of drawing along with it, I’m not sure, but I bet you could drop a postage-paid postcard in the bag and then the folks could just drop it in the mail if that was easier for them.