I love the way Ursula LeGuin builds alternate worlds. She makes them differ from ours in meaningful ways, she changes things we take for granted and explores the consequences of the differences well. I want to read more of her sci-fi work.

The Left Hand of Darkness was a great book, all in all. It tells the story of an envoy of an interplanetary cultural and economic league, called the Ekumen, to the planet called Winter (or Gethen, by the locals), whose inhabitants, though humanoid, don't have a set sex: they go in heat once a month, and then their body temporarily chooses a sex practically arbitrarily. The same person could perform as male one month, and then get pregnant the next. The planet is also much colder than Earth, and thus practically in perpetual winter.

Genly Ai, the envoy, is caught in a very intricate web of intrigue and politics, trying to get the rulers he encounters to accept the Ekumen and join it.

LeGuin uses language deftly, mixing English with made up words in precisely the right amounts - for example, she uses "native" Gethenian words for concepts that don't easily translate to English, as they are alien to us, and very central to Gethenian culture.

As I mentioned above, the world building was also great. LeGuin manages to describe more than one Gethenian culture, and manages to separate them from each other, and also make them reasonable and unique.

Finally, I loved how the book tries to explore gender by positing this hypothetical humanoid race and trying to make sense of the different societal structures that could arise from it. My only gripe with this element is that the narrator often comments on the natives using pretty dated and somewhat sexist ideas about the sexes. I guess this can be explained away by an unreliable narrator, or by the fact that the book was first published in 1969. In any case, even though a bit off putting for a book that has such a revolutionary take on gender, this flaw is sparse and I could overlook it.