One of our longest-standing debates is over Frank Herbert in general and Dune in particular. The coz is Herbert's most enthusiastic cheerleader, and I can see his point of view: if you can skip over the unintentionally hilarious homoeroticism of a bunch of manly men riding giant worms together, Dune has a lot to love. The technology and the backstory are interesting and detailed, the atmosphere is immersive, and Herbert pulls no punches when it comes to killing off half the cast of characters within the first quarter of the book, including some of the ones it's clear Herbert himself really liked. This is not easy for a fiction writer to do.
I'll try to limit the spoilers from here on out. Brief teaser for anyone who hasn't read the book or seen the movies: Paul Atreides is the scion of a noble house which has just been given the governorship of Arrakis, a desert planet which is the universe's only source of a spice that indirectly makes space travel possible. This seeming honor, coming as it does with the opportunity to make a hell of a profit, is actually a double-edged sword, and it seems that the Padishah Emperor, Shaddam IV, might have it in for Paul's father, Duke Leto. Meanwhile, back on the ranch, Arrakis is inhabited by the Fremen, a mysterious race which manages to live in the desert despite the general opinion of everyone else that it's impossible. Oh, and there are giant worms that live in the desert and pop out and kill everybody all the time, which is awesome.
That's the scenario. I hope it makes the book sound appealingly interesting, because it is: it's one of the most solid sci-fi tomes out there, and not just in the sense that it's big enough to stop a door with.
The reason I'm not on board with the rah-rah-Herbert program isn't the plot, and it's definitely not the world-building, and it's not even the characters, per se. The problem is that Herbert wasn't satisfied with writing one of the most entertainingly inventive science fiction novels ever. He wanted to write something philosophically meaningful. This is a bad idea 99% of the time, and when the author intends to write something with deep meaning, rather than simply doing it by accident, it's a bad idea 100% of the time.
Bottom line: Herbert was not as smart as he thought he was. In Dune, he makes the same mistake that Orson Scott Card commits in Ender's Game and in most of its sequels*: he assumes that when he uses his utmost mental acuity to construct super-genius characters, he a) is not limited by his own intelligence in how intelligent his characters can be, and b) is smarter than all of his readers. Or one of the above. I can't actually tell if Herbert and Card think they're smarter than everyone, or just think (wrongly) that they can convincingly write characters much smarter than they are, but the end result is a bunch of disappointingly obvious conclusions arrived at by genius characters who were slower to find the answer than many of the readers.
The only author in my experience who managed to write a convincing super-genius character was in fact Arthur Conan Doyle with Sherlock Holmes. Conan Doyle, first of all, was clearly smarter than most, and then he used some clever literary tricks to pull off a character even smarter than he himself was. That's for another day, though.
I give Dune a solid four stars overall. I give the David Lynch film version four stars as well; the trailer will make it clear why, but: Kyle MacLachlan. Sting. Manly men riding giant worms together to the strains of the best 80s guitar ever wailed. Kyle MacLachlan and Sting fighting each other with knives. Read the book and watch the movie, but for the love of God don't read the Dune sequels unless you really enjoy books that aren't very good, like I clearly do.
*The mistake that Orson Scott Card made with the Ender's Game sequels that aren't kind of unjustifiably condescending is that they really suck. Speaker for the Dead, I'm looking at you.