[banjobama]

You could make a shelf called "Read" and move the read books onto it, if you don't want to root your Nook. This is similar to what I do with my Sony. I like to keep the books on the device but I have a collection called Read that I move them to once I'm finished reading them.

Edit: actually, this won't remove the books from the main screen, so it might not help you. I didn't think of that before.