Dune is one of the books I reread every few years. It's just an amazing book, with powerful characters and lots of big ideas going on.
I've probably read it five or six times now, and I felt like reading it again, recently.
The main thing I end up wanting to talk about, though, is the copy I was reading. My old copy was a thirty-five year old paperback that I bought used, some time ago. Not wanting to keep tearing it up by reading it, I bought a hardback edition not too long ago (I'm pretty gentle on my books, but that's getting so old, especially for a paperback, that it seemed time).
I can't remember where I got it, unfortunately, but it's not a very good copy. They obviously didn't have the same material to work from, and appear to have run an older copy through a scanner (with OCR) and a dictionary, and not done much else. This led to numerous words that changed (some that I compared were and->arid, cave->eave, Chani->Chard), that were correct in the original edition. Two other, minor changes occurred with the chapter breaks as well: there were now page breaks at the chapter break, and the source of the quotation at the beginning of each chapter was no longer bolded.
Odd, all the way around. You'd think the book would sell well enough to be more careful with these things.
One thing that didn't occur to me, the first several times I read the book (though it wasn't on this reading that it hit me) was the talk about Mentats being people who were faster than computers. In my lifetime, that's pretty much impossible (particularly for calculations), but eventually it occurred to me to think when this was written in the mid-sixties, when that was possible.
The reason I bring this up, is that I wonder if there are other .... anomalies, maybe? I'm not sure what to call them.
One thing that did only occur to me on this reading was to wonder if Herbert had any appreciation for the limitations of infrastructure. It seemed to me that the technology ascribed to the Fremen in the book would require far more infrastructure than was available. It would also seem to require far more education (even if only within a small caste) than was apparent in the descriptions. Especially think about requirements for digging these vast caverns, and about moving everyone from one sietch to another. Both of those would require heavy equipment. There's a reason there aren't large-scale civilizations underground anywhere on earth.
Still, despite those niggling thoughts, a fantastic book of amazing sweep and scope (especially given the page count. A similar book, written today, would probably have 2-300 more pages).
I'm not going to talk about them in any detail right now, but I have read the three direct sequels. The middle two I don't really remember. The fourth I remember liking quite a bit, though it had a lot more in it of religion. I would expect the fourth to get very polarizing reactions, either of love or hate.
Update: Just to add to what I was saying about infrastructure, two notes. One, every factory would need to be duplicated in every sietch, and two, factories would leave visible signs when abandoned.
And it just now occurs to me that getting a palanquin on top of a maker would be just about impossible. Think about how people got on top, then think about the possibility of going up (and down) that way while carrying a large platform.