I've commented before on reading as a cheap pastime. I'd like to emphasize one of the things that can make it so cheap: library book sales.
I'm lucky to work in walking distance to both a university library bookstore and the bookstore of the friends of our local public library. Yesterday I bought Jen an omnibus of 5 M.F.K. Fisher books for 50¢. The last book I read was an annotated autobiography of Ben Franklin. 5¢. I have a stack of other good books purchased for 5-75¢. See if your town has any standing library book sales; if it doesn't, find out when your local library has its sales.
I've seen some e-book enthusiasts bashing physical book readers with accusations ranging from being out of touch to outright luddism. And for all the considerable advantages e-books offer, physical books retain the killer feature of being available on the cheap. Get back to me when you can buy desirable in-copyright used works for 5¢ for your e-reader.