I guess that I am in cdfox's camp. If you are reading something that you enjoy, you will read more and are more likely to try and figure out those unfamiliar words. My DD12 reads voraciously so I am not worried about her vocabulary. She plowed through The Hunger Games in a few hours and went on to read other books, lots of them, some with advanced vocabulary, some not. If I had told her to read Red Badge of Courage, she probably would still be slogging through it and resenting every minute of it. It's just not her kind of book.
For the record, I hated Wuthering Heights and will tell my kids to avoid it like the plague until they have to read it for a literature class.
