The Left Hand of Darkness is one of my favourite sci-fi novels.
Le Guin's world building in it is exceptional in that it covers so many aspects - politics, religion, underlying mythology, anatomy, architecture, weather, as well as science - but also manages to be consistent across all these ideas, making the whole a believable construct.
But more importantly she was a great story-teller. The trials of the journey across the ice are vivid, the short stories of myths dotted throughout the novel are perfect in their imperfections, as myths tend to be. And Genly's inability to understand Estraven's honour or in fact any of the polictical actions fit perfectly with his role of envoy.
A wonderful novel by a wonderful author.
Excellent comment. I love the term "world building" because that sums up one of her major strengths.