This is an overwhelmingly excellent book.
On the planet Gethen, also called Winter, humanity exists in a unique form - all Getheninans are androgynes. Genderless most of the time, a Gethenian may become either male or female each month, during the three-day-long kemmer period.
The societies that developed in this unique strain of humanity are explored by the author intelligently and sensitively. Ursula Le Guin has a rare talent - she can make the most familiar exotic, and most exotic, familiar. I am not the first reader of this book to wish for a chance to visit Gethen.
Set in the Hainish Ekumen long after the overthrow of the Shing, (look for other books in the Hainish series: The Dispossesed, Rocanon's World, Planet of Exile, and City of Illusion,) The Left Hand of Darkness tells the story of Genly Ai, First Envoy of the Ekumen to Gethen. It is also the story of Therem Harth rem ir Estraven, a high official of the Gethenian Kingdom of Karhide, called the Traitor, the truest and most loyal citizen Gethen has ever known.
The Left Hand of Darkness tells a captivating story of fidelity and betreyal, set in a world that is alien yet familiar to us. Ursula K. Le Guin's unique writing and incredible imagination make reading this book an experience unparalelled in any genre.
I only wish I could give more than five stars.