Re: Dune - The Book and the 1984 film *spoilers for both*
Heretics and Chapterhouse can be difficult to get into at first, because of all the new characters. Once you get past that, I think they are enjoyable and thought-provoking. The image of the BG Reverend Mother with the Van Gogh painting on her wall has stuck with me.
"In the name of the best within you, do not sacrifice this world to those who are its worst."