To me, Dune is some new-age mumbo jumbo. It's fanatasy in space. Or it is contemporary social criticism (the whole thing is a metaphor for the oil industry, no?), but it's definitely not sci-fi.
By the way, I loved the first half of the book. The world building is fantastic, the characters are interesting (and the villains are really villain-y) but after the Duke dies, the whole book goes down the toilet and becomes a series of random adventure-in-the-desert encounters that couldn't be more shallow and predictable.
That being said, I'm probably too young to get it's larger impact on the "genre" (I heard that it's something like the defining space opera?).
the whole thing is a metaphor for the oil industry, no?
No, not really, or at least I think not deliberately; it's much more Lawrence of Arabia in space.