The Left Hand of Darkness was written in 1969 and before long will celebrate its 50th anniversary. I first read it as a teenager, and I have gone back and reread it several times since then, each time adding more to my appreciation.
The story is set on the cold planet of Gethen, which is inhabited by a race of intersex humanoids: people who have both male and female characteristics and genitalia. Any one of them can become pregnant, any one of them can inseminate. To this place comes an adult male envoy from the Ekumen, an outside authority. This is Genly Ai, who appears to the locals as a Pervert, as he is unable to shift into a female phase.
Quite apart from exploring gender stereotypes and human relations, the book also goes into the theme of xenophobia, both in the locals’ attitude towards Genly Ai and in the local war between two neighbouring nations on Gethen. There is a strong theme of treachery and what it really means to be a traitor, how this can be seen from different perspectives. This all leads into the relationship between Genly Ai and the Gethenian Estraven, a central strand woven into the story. Their relationship is beautifully examined, and I found the reactions and behaviour of both very realistic and believable. These are not just credible characters; they really come alive.
Le Guin provides a wealth of rich detail for her planet: there are allusions to its history, its mythology, and the local culture is well described and realistic. This is a book that can be taken in many ways: as a simple science fiction novel, as a political text, as social commentary, or even as a story of friendship, and its versatility is that it works well in all of those fields.
This is an incredible book, and one I expect to read again.