That and the names. I did read somewhere that Herbert studied desert ecology and desert cultures as research for the book. I just couldn't get into it. However, the popularity of Dune did put a couple of hundred bucks into my pocket. It was a mint condition Dune Encyclopedia that the flea market lady sold for just a buck. A few months later, some other flea market person offered me the same book for $10 and was shocked when I flipped out a ten-spot to pay for the book without any attempt to negotiate the price like about every other flea market buyer would have done.
Well, that would make sense if one were going to write a book based in a desert landscape.