A reread from my teenage years... Now noticing the flaws in the writing and the plotting, but still enamored with the universe. Fills my main request for a "science-fantasy" book, i.e. provides fodder for daydreaming!
Dune. The best stand alone science fiction book ever. Do not bother with the so-called sequels; they are unnecessary and poorly written. Another pinner wrote "Best book ever written." Hard to disagree with that.