The premise: in the somewhat-distant future, a benevolent trade league unites planets descended from proto-humans who colonized the galaxy a few million years ago. The protagonist, Genly Ai, is a human (Terran) dispatched by the league to make contact with humans on an icy planet called Gethen. The big twist is that the Gethenians don't have binary sexes -- everyone has a monthly cycle where they semi-randomly take on a male or female reproductive role for a few days.

To do his job, Genly has to learn to navigate Gethenian politics & culture. The plot is thus neatly aligned with the novel's real interest, worldbuilding. As the novel unfolds, we learn how the Gethenians dress, plan their cities, raise their kids, organize politically, punish criminals, have sex, think about technological change, worship, fight, and more. This comes partly from details in the narrative and partly from interstitial documents contextualizing it (myths and legends, historical notes, even a medical report, all of which are well-written and believable). Given the breadth of topics, it's impressive that none of it felt encyclopedic, tedious or self-indulgent.

One of the ways speculative worldbuilding can have literary value (I think) is when it leads us to reflect on the unconscious assembly of our own 'real' world from the details of daily experience. A lesser writer might have written this as Earth II: Enby Edition, but by setting her fictional societies in an extreme environment, LeGuin invites the reader to think critically about which details are attributable to genderless society, which are attributable to the natural history of their frigid planet, and which are purely contingent.

Genly's narrative lens underscores this. When starting the book I had been curious if it anticipated any of the ways we've come to think & speak about non-binary/trans/intersex people, but in retrospect I think it's really about the gulf in understanding between men & women, crystallized in the moment when Genly's Gethenian foil asks him to describe Terran women and he gives a believable but very stupid answer. Thankfully, it is a hopeful novel, never abandoning the possibility that profound difference can coexist with understanding & love.

Lastly, I've come to appreciate LeGuin's writing style a bit more with each novel I read. It's unpretentious but willing to indulge in lyrical passages where appropriate. Scenes are chosen deftly; an impressive amount of 'world' is packed into a fairly slim book. And above all, she always writes like someone with something to say.