Mat Linnett wrote:... the first one's fantastic, but the rest get progressively worse...
most of SF is 'worse' than Dune. the other 5 books in the series are pretty good, especially Children of Dune, but not so much God Emperor of Dune, in which not enough really happens until the end
the Dune books to *really* avoid like the plague are Brian Herbert's (Frank's son) stab at completing Dune 7 (which existed as 1000 pages of notes): Hunters of Dune and Sandworms of Dune; utter pieces of shit, poorly written and the guy makes up a pisspoor excuse to resurrect all the original Dune characters but lack's Frank Herbert's skillz
likewise, avoid all the satellite works by Brian Herbert, the Butlerian Jihad etc. the guy is a talentless hack with the prose style of a mills and boon writer