I remember reading about an experiment in which they did exactly that: change the text on a computer screen during eye sucades, when the eyes aren't processing data, IE while you're "Not looking". Which reminded me of trying to read in dreams, certainly.

I once had a lucid dream in which I decided to see how good my latent memory was by picking up a book from my self in the dream and reading the first line to see, when I woke, if I'd got it right. But it was just nonsense babble which, as you point out, kept changing. Oh well.