Yeah, the series just gets less accessible as it goes on. I do love the story of Messiah, even if things get a bit lost in translation from Herbert's mind to the page, but by Children of Dune it starts getting almost un-understandable! Children of Dune is a good place to leave off, though, because it's the end of what Herbert thought of as the first 'trilogy'. Interesting reads, but not what I would describe as 'fun' haha