Dune has incredibly memorable world-building. It’s clear that Herbert put a lot of time in building the mythology and the setting of Arrakis, and the result is a lived-in world rich in detail. The only problem is that he can’t really write! The ending, where Paul kills Feyd-Rautha, is terribly anticlimactic! Why must we know what everyone is thinking all the time---isn’t it obvious from context? Let’s introduce concepts (jihad) without really fully explaining them.
I still like the book, but more for its overall setting than its plot or writing.