Frank Herbert wrote the first six of the series. I have read all of these six. The remaining books, I'm not sure how many, quite a few, were co-written by Herbert's son and another writer. I haven't read any of those.
The first one comes across as a star wars-type adventure with a hero's story, but as you make your way through the rest, you realize it is a harshly critical portrayal or societal problems, placed in a science-fiction universe. Heroes, charismatic leaders, use of religion as a control mechanism, ecological disaster, sexual roles, you name it, Herbert really had a lot of social commentary.
Some, after reading the first novel, have claimed it was just another version of the White Savior theme. Just reading the first one might give that impression, but the remaining novels, if read, make it clearer that it is a criticism and damnation of the charismatic leader theme.