While this book is far shorter than the first, it is far more complex plotwise. While the first Dune was a Hero’s journey, Dune Messiah takes that premise (along with the Messiah) and deconstructs to the fiber of it’s being and concept.
I felt in the first novel that the world established most of the philosophy and politics, while in Messiah the philosophy and politics come from the characters. Messiah is far more focused on the inter-personal relationships and conflicts of the characters than anything. Most science fiction would, but most of the focuse on wars and battles that are established to be happending in the universe.
Here we do not personally see them, but feel the effects that the characters go through because of them. We see some personal questions and the some tough ideas explored through Paul and nearly everyone else involved.
Dune Messiah is a character driven work that is greatly complex. I needed to take a break from the Dune series after reading it