It's been a long time since I read the initial trilogy, and i agree the sequels (including Messiah and Children) were not really worth reading (not so much for weirdness as just not being interesting). It seems, however, that the themes Herbert claims drove the book really only come into play in the sequels. The first book is a standard story of revenge and a good, handsome, plucky underdog overcoming the fat, deformed, seethingly evil bad guy against all odds. Where's the heroes are fallible stuff? In the far less compelling sequels.
Herbert wrote the first book as multiple novellas, serialized for publication by Analog. His later novels are much looser, and clearly didn't benefit from the attention he put into making sure the originals would be accepted by the leading science fiction publisher of the time.
