The Left Hand of Darkness is part of the Hainish Cycle, but very much as a standalone novel. Humanity is scattered among dozens of worlds. The planet Gethen, also known as Winter, was colonized by humanity many thousands of years previously. Contact was then lost and has only recently been re-established, with the Ekumen, a sort of federation of worlds, sending an envoy to bring the world into the fold. It is through the eyes of this envoy that most of the story is told. The humans on Gethen show curious sexual characteristics, spending most of their time as androgynous non-sexual beings, then entering a period of estrus once a month, at which point they become either dominantly male or female. This changes gender politics entirely, in fact eliminating them completely. On Gethen, people are judged on ability, with gender not entering into the equation.
While the premise is interesting, the novel has two problems. First and foremost, it may have been rather progressive when it was published in 1969, but nowadays the exploration of the human sexuality issue that is at the core of the novel is both dated and non-subversive. The world has moved on and the novel has aged badly because of it. Secondly, it is rather dull. I never felt that I cared either way for the envoy or his mission, or if the two depicted nations on Gethen would go to war. The characters are dull and the world is dull. The stakes are nominally high, but the setting is washed out and feels dead to the reader. I gave up about a third of the way in.