Here’s the original series of 6 novels by Frank Herbert, each IMHO weaker and more confusing than the last:
Dune (1965)
Dune Messiah (1969)
Children of Dune (1976)
God Emperor of Dune (1981)
Heretics of Dune (1984)
Chapterhouse Dune (1985)
Much later Frank’s son Brian Herbert and science fiction author Kevin J. Anderson expanded the series, adding many new books. They try to make sense of Frank’s vision.
I’ve now read 6 of the dozen or more Dune books in chronological order:
• Dune: House Atreides (Brian Herbert & Kevin J. Anderson)
• Dune: House Harkonnen (Brian Herbert & Kevin J. Anderson)
• Dune: House Corrino (Brian Herbert & Kevin J. Anderson)
• Paul of Dune (Brian Herbert & Kevin J. Anderson)
• Dune (Frank Herbert)
• Dune Messiah (Frank Herbert)
Frank was a genius in conceiving Dune, I concede.
But the son’s books are far better, more accessible, than his Dad’s.
In Dune Messiah, for example, almost nothing happens … aside from a poorly unexplained nuclear explosion that seems to do no damage except render those nearest to it blind. Was Frank a mad genius? … There was something wrong with his brain, I’m thinking.
I’m not burned out yet. Next up is Winds of Dune.
Last I’ll read the 3 earliest books, the prequels, which look to be excellent.
Rick McCharles 
> In Dune Messiah, for example, almost nothing happens … aside from a poorly unexplained nuclear explosion that seems to do no damage except render those nearest to it blind. Was Frank a mad genius? … There was something wrong with his brain, I’m thinking.
Well, I guess it’s a good thing that KJA and BH write for the grade school, because that suits you admirably. If that’s all you think happened in DM, then you’d better stick to simpler fare rather than try to judge Herbert’s work. I shudder to think what you would make of an even more sophisticated writer like China Mieville or Gene Wolfe.