O-kay... Warpus, I spent several years on Dune forums - admin'd a couple of them for awhile, and things went okay until the nuDune books came out and fandom promptly split into several different factions.@illram, Don'te listen to Valka, the prequels/sequels written by the son and the other guy aren't that bad
You will probably not enjoy them if you go in expecting Frank Herbert though, his writing style can not be matched.. if you go in expecting a light space opera type story, then you might have a good time, circumstances depending.
The stories definitely have everything to do with the original 6 novels. But either way I wouldn't call any of Dune hard science fiction.
But ya, the KJA/Herbert Jr. novels are not horrible. People who hang out on Dune forums seem to hate them though, you'll run into a lot of people on there who are just obsessed with the subject (not you Valka, you're cool!). It's sort of like the whole hate of ENterprise & the JJ reboot you'll see discussed on Trek forums. Die hard Trek fans who care too much about canon pile up tons of hate on them. They are out of control. The novels can be enjoyed if you go in expecting the right thing.
The nuDune books (anything with Kevin J. Anderson/Brian Herbert's) names on them ARE horrible. They're badly written, badly plotted, the characters are basically caricatures, KJA/BH completely missed the whole point of the Butlerian Jihad, they retconned the entirety of the original Dune novel that FRANK HERBERT wrote into some "propaganda tract" Paul ordered Irulan to write, and that goddamn Norma Cenva is the worst deus-ex-machina plot device I have ever seen!

Paul was NOT born on Kaitain, and he and Bronso of Ix did NOT run away on a Guild Heighliner and join the circus when Paul was 12 (it states clearly in Dune that the crossing to Arrakis was the first time Paul had ever been off Caladan, and it was also made plain that he was born there). Duncan Idaho's first battle in the Atreides' service was on Grumman, not as part of that nonsense KJA/BH wrote.
The Butlerian Jihad was NOT about fighting "thinking machines." It was an Imperium-wide civil war of pro-computer/thinking machine humans vs. anti-computer/thinking machine humans. It was a war of ideology that became a religious war, and we all know how long those can drag on, right?
The mess they made of "Dune 7" - the Hunters/Sandworms books - shows they weren't paying attention to the previous two books. The question of who Marty and Daniel were is obvious: They were the next step in Face Dancer evolution. They were NOT Erasmus and Omnius, who were merely a couple of robots invented by KJA/BH to control the other machines that ran around like the Dune version of Terminators.
And I take a rather dim view of a professional author (Kevin J. Anderson) referring to people who don't like his books as "Talifans."