Dune Messiah was a disappointing follow-up
Up front, Messiah felt like it lacked depth. The conflict is there and in multiple directions, but it doesn't feel like it's actually gone into in any real detail. Character development feels the same way, moments are short, lacking fullness about them that you feel the actual development. The prose and style of narration are different. It feels less like a proper sequel and more like something convenient to write about.
I do want to take a moment and talk about a letter from Brian that's at the front of the copy I had. He talks about how people felt that Messiah is bad because it's not about Hero of Arrakis Muad'Dib, rather it talks about a lot of the negatives and darkness associated with Paul. He goes on to call out a few small moments from Dune about the problems to be had with such a Hero and why Paul shouldn't be seen as one at all. To me that felt apparent anyway, because while there's still a lot of "Hell yeah, get your revenge" in Dune Paul talks about the fear of his Jihad that he cannot stop, and it's also not terribly shocking you're not exactly a good guy if you hold the galaxy hostage in destruction of a major product to coerce your way to being Emperor.
It's still alright there's still parts and pieces that I did like, but it left me uncertain which side of the execution I'm getting with Children of Dune.