Dune Messiah is relatively simple to do compared to subsequent novels. It's almost an extension of the original Dune.

But even with Dune 1/2, I talked to many people who haven't read the novels and they found Dune 2 confusing. Dune 1 was like the first ~20% of the book. The last 80% of the story needed more; how I wish Villeneuve had the opportunity to make a full trilogy.

I am worried that beyond Dune: Messiah, it will become increasingly difficult to make a good movie adoption. Children and God Emperor are probably easier, Chapterhouse and Heretics will likely be very challenging.