I did this to a bookcase once. I used a cafe curtain rod and the brackets that came with it. Just attach the brackets at the top of the shelf on either side of it and hang the curtain from the rod.
I love the idea of using curtain rods. You could start with using a tension rod and putting a curtain in place to get an idea if how it would look before attaching a permanent rod. Have fun with this project!
Another idea would be to attach a piece of wire or strong string or cable from nails, screws, or eyelets