This book won the 1969 Nebula Award and the 1970 Hugo Award for best science fiction novel of the year. I recall first reading this book when it first appeared and being stunned at the originality and the beauty. I have read every Hugo and Nebula winner (and most of the nominees) and this is still near the top. In this classic novel, all of the action takes place on the planet known as Gethen or Winter, a frozen world set in Le Guin's Hainish universe. All of the humanoid inhabitants of Winter are exactly the same as the humans of Earth except in the means of reproduction. They are all of a single sex and can assume either sex when in "heat." If one person of a couple becomes female, the other automatically becomes male. The culture and society of this world is shaped not only by the harsh environment but by this sexual structure. A main portion of the novel is concerned with the trek of a human ambassador and ethnologist, Genly Ai, across Winter's surface with a Getthenian. The man from Earth and the manwoman from Winter grow to know and understand each other. The novel not only raises issues about our perceptions of sex but the problems associated with cultural chauvinism. It is a book that all serious students of science fiction literature should read. For those earlier reviewers who awarded this book a low rating because it wasn't "classic" science fiction, you have to recall that psychology, sociology, and anthropology are all sciences (remember that the author's father, T. Kroeber, was the first Chairman of the Anthropology Department at U.C. Berkeley), just like physics, chemistry, or, in my case, biochemistry. And to the reviewer from Washington, D.C., (of March 3, 1999) who complained that Genly Ai was too uninteresting as the main character. Perhaps that was the point. Have you forgotten your Heisenberg?