Genly Ai is a human male, from Terra (Earth). He is an envoy to the planet Gethen, representing a coalition of planets called the Ekumen. Gethen is populated by creatures much like humans, but are neutral gendered, and can choose to switch to either male or female based on circumstances.
Genly lands in a kingdom called Karhide, and hopes to appeal to the king to initiate the proceedings to include Gethen into the Ekumen. With the help of the prime minister Estraven, Genly seems to be making good progress, when he is suddenly rebuffed and Estraven is exiled.
Genly travels to the fastness, where it is predicted that Gethen will indeed join the Ekumen within five years. Encouraged, Genly travels to the neighboring kingdom of Orgoreyn, where the politicians are initially very receptive, because they had been primed by Estraven. But the secret police, which controls the kingdom, arrest and send both Estraven and Genly to a prison camp in the far north.
Genly and Estraven escape and make the arduous trek back to Karhide, where Estraven predicts Genly’s appearance will shake things up. During the journey they form a close bond, and Genly teaches Estraven mindspeak, the language of Ekumen.
They reach Karhide, but are betrayed and Estraven is killed. As predicted, Genly’s appearance causes the governments of both nations to fall, and the new governments agree to join the Ekumen.
Vast in scope with detailed and nuanced world-building, this book is part of the Hainish cycle. The author describes the squeamishness felt by both the human, as well as the aliens of Gethen, when encountering a creature quite different from themselves. The close bond which is formed, and the redemption arc are wonderfully written and a joy to read. Strongly recommend.