Speaking Those Future Words
Herbert's writing style is pretty straightforward, with one huge not-so-straight-forward exception. Let's get the basics out of the way first.
Madame Plain Jane
Herbert's scenes generally follow a basic formula: he'll have a few characters walk into a room, write a few sentences giving the details, and then let the characters talk. Even in crazier scenes, like Paul's gom jabbar test in Chapter 1, dwell in the realm of the comprehensible due to Herbert's use of manageable sentences and his reader-friendly word choices. Take a look:
Curiosity reduced Paul's fear to a manageable level. He heard truth in the old woman's voice, no denying it. If his mother stood guard out there… if this were truly a test…. And whatever it was, he knew himself caught in it,[…] (1.82)
See, pretty basic stuff. Herbert's sentences mostly build off of noun + verb independent clauses with dependent clauses attached to the beginning or end of the sentence. Even his odd use of the ellipsis above won't throw you, because the concise word choice makes for an easy transition.
Well… mostly concise word choice, that is.
A Bonk to the Nonce
As a genre, science fiction's got a love affair with something called the nonce word. That's a word created for a specific context that will probably never come up again. For example, in Strangers in a Strange Land, Robert Heinlein needed a word to describe the Martian phenomenon of fully comprehending another person or thing. Such a word didn't already exist in the English language—why would it?—so he coined the verb to grok. And boom, a nonce word is born. Care for another example? Lewis Carroll composed his poem "Jabberwocky" almost entirely out of nonce words.
And Frank Herbert, well, the man loves his nonce words. Loves them! Odd words such as bakka, fremkit, lasgun, and varota litter the novel's pages. Lucky for us, the context usually provides the gist of the nonce word. When the Baron asks Piter if he's been chewing verite or semuta, the reader can probably guess those are both futuristic drugs (2.30). But you'll have to look in the appendix or Dune encyclopedia if you want to know that semuta is a narcotic derived from elacca wood—or what elacca wood is, for that matter.