God-Emperor of Dune is a deeply intellectual book.
I thought Dune was okay. I liked it an average amount, though it was not an average book. It simply strayed from the norm in ways I found canceled each other out. I actively disliked Dune: Messiah. The things that Dune did averagely or badly, it did worse, and it did not do other things better.
I first saw the change in Children of Dune. I found the first part of the book boring, though it was helped by having quite a bit of interesting tension and more int. After that first part, the tension didn't fade, but the worldbuilding and characters grew even more interesting. I found it thought provoking, but, as with the previous books, I didn't really like the plot.
God-Emperor of Dune carried through everything that Children did right, but it had an interesting plot, the most interesting and compelling character I've ever read (the primary character that first appeared in Messiah, to not give spoilers), one of the most interesting characters I've ever read (other major viewpoint that was introduced all the way back in the first book), and some of the most intriguing thought experiments I've ever seen. Legitimate 10/10, I will 100% be reading it again, and thinking about it until I do.