I propose a weighted star rating system. Specifically, I don't think a DNF 1 star rating should be given the same weight in a rating. Many literary classics are rated much lower than "crowd pleasers" and perusing the ratings, it seems like some of this may be due to people marking DNF and citing everything from form to content to issues with characters not being likable to give a poor rating. I think a "% DNF" would be a good metric to still give those people a voice, but rating a book after reading 1/4 of it is silly.