Here's an example of QR codes being used in a way you might not have seen before:
From their website:
Books2Barcodes is an ongoing effort to convert all the world's great books to QR codes (2D barcodes). Each work featured here is the entire text of a piece of classic literature translated into several thousand barcodes. With a mobile device equipped with a camera and a barcode-scanning app, you can experience the joy of a great book as read through 800-character fragments on your cellphone.
You might see this and respond like I did, "Why would anybody do this?" Obviously, this is not the use intended when QR codes were first used at an automotive assembly plant to keep track of parts more efficiently; you can read more about their history at http://en.wikipedia.org/wiki/QR_Code if you'd like. Considering that, I see this as a proof of concept, rather than an implication that this is the future of the medium.
It is possible, of course, that books and QR codes could be intertwined in a library or bookstore environment in ways that are more sensical. Imagine the example of walking out the door with synopses and citations without writing anything down. But the possibilities for text embedded in a QR code go on.
Perhaps consider a course syllabus stamped on the inside of a course text, letting the student recall today's class topic without fumbling through a folder. How about ingredient lists (or even a full recipe) under buffet tables? I could also picture easy-scan nametags at conferences, so you could scan one another's nametag and avoid the pile of business cards that get lost on the way home.
Have I missed anything? Feel free to add your ideas.