The Left Hand of Darkness is my favorite Ursula K. Le Guin novel, and quite possibly my favorite of all SF novels.
I’ve read the novel many times, delighting in Le Guin’s prose and admiring how she unapologetically immerses her readers in the world, minus expository cliffnotes, so that our experience is akin to Genly Ai’s first contact—everything at once, swamped with alien mystery, so that from the very first we have to puzzle our way along, piecing together the layers of significance and meaning.
And when we shift to Estraven’s native point of view, and see Estraven puzzling over Genly, and then shift to the Gethenian folklore, and layers build on layers of meaning, and the two characters come together, struggling to connect—oh, I’m swept away.
That’s what I love about the best science fiction: it takes me there.