This review will contain spoilers!
In many sentences:
This is actually the second time I've read Dune, the first being several years ago in college. While I still enjoyed it, I remember enjoying it more the first time than I did this time. I'm not sure if it's that my tastes have changed significantly, or if I'm simply reading with a more critical eye now that I know I'll be discussing a book afterwards. Either way, Dune is an enjoyable, clever book that I find lacks the subtlety it would require to make it a nearly flawless work of fiction.
My primary criticism, and the reason I say it lacks subtlety, is Herbert's use of the inner monologue that characters have to convey information, emotions, and motives. Throughout the book, we are privy to the inner dialogue of various characters. Literally, we are able to read their thoughts. While this is useful, as we are able to see exactly what the character is thinking at a critical moment, it struck me as a cheap way for Herbert to get important information across to the reader. This is especially disappointing because, otherwise, Dune is a masterpiece. In fact, within the book itself we see Herbert revealing information more subtly than we do here.
At the start of each chapter is an excerpt from one of the many books Princess Irulan will ultimately write about Paul. It's ironic because, while our glimpses into the thoughts of the characters are a heavy-handed technique to provide information, the pre-chapter excerpts are a lesson in subtlety. How can Herbert execute one aspect so perfectly, and another so poorly? It's another situation (like Fall of Hyperion's perspective changes vs. East of Eden's) where one thing is done so well that it only serves to highlight the mistakes. Speaking of these pre-chapter interludes, I imagine this is where Orson Scott Card got the idea for his Ender books? Even if it is, I don't think that detracts from the Ender works since they are still executed well.
The last thing I want to mention is the sections where Paul and his mother must deal with the issues of prescience and multiple consciousnesses. While most of the book is well-written, these sections really shine. Considering this is an extremely difficult concept to understand, the fact that Herbert not only writes it so I can follow what he's saying, but that he does so with enough clarity to bring it to life vividly in my mind is impressive. In fact, I get the feeling that this is really the story that Herbert wanted to tell, and everything else is there just to give us a context for this subject. Granted, it's easy to say this with the foreknowledge that genetic memory becomes a crucial component of the rest of the series, I think the skill with which Herbert writes these parts only reinforces how important they were to him.
Dune is understandably considered one of science fiction's great masterpieces. It is a well-written, entertaining book with a unique concept that is thoroughly realized. However, considering its flaws, such as the heavy-handed approach of reading each character's thoughts, it is also understandable why it is not often considered a masterpiece of fiction as a whole.
Small aside - I remember thinking in college that there was a connection between Dune (or perhaps the series as a whole) and Plato's Republic. I haven't read the Republic in years, but I wonder if that connection is still valid?
Frank Herbert the First Line of Dune