I really like the leather cover for the Cybook. It protects it well, is discreet and even gives that hug a book feel. I was reading in a coffee shop and one of the workers walked by me about 5 times and on the 6th time stopped and said "OMG what is that is that? Is that ever cool, I thought you were just reading a journal."
I hadn't thought about the vegetarian angle though so it's good that you speak up and let the manufacturers know because they probably don't think about it either. If someone came out with a hemp cloth cover for it I'd probably buy it as a second cover. If I'm covered in suntan lotion I probably wouldn't want to be holding the leather cover. Of course I'd want mine laden with THC so that it would dull my pain if the device ever goes up in flames.