[10] In 1987, Locus ranked it second among science fiction novels, after Dune,[11] and literary critic Harold Bloom wrote, "Le Guin, more than Tolkien, has raised fantasy into high literature, for our time".

[19] Le Guin has also said that the genre in general allows exploration of the "real" world through metaphors and complex stories, and that science fiction can use imaginary situations to comment on human behaviors and relationships.

But it gave me the courage to ask the agent Virginia Kidd, who had praised one of my earlier books, if she’d consider trying to place The Left Hand of Darkness as a hardcover.

The people of Hain colonized many neighboring planetary systems, including Terra (Earth) and Gethen, possibly a million years before the setting of the novels.

[22] This galactic civilization is known as the "League of All Worlds" in works set earlier in the chronology of the series, and has been reconstructed as the "Ekumen" by the time the events in The Left Hand of Darkness take place.

[4] The protagonist of the novel, the envoy Genly Ai, is on a planet called Winter ("Gethen" in the language of its own people) to convince the citizens to join the Ekumen.

[24] The inhabitants of Gethen are ambisexual humans; for twenty-four days (a period called somer in Karhidish, a Gethenian language) of each twenty-six-day lunar cycle, they are sexually latent androgynes.

This absence of fixed gender characteristics led Le Guin to portray Gethen as a society without war, and also without sexuality as a continuous factor in social relationships.

[36] Rescued by Estraven, the deposed Prime Minister of Karhide, Genly realizes that cultural differences—specifically shifgrethor, gender roles and Gethenian sexuality—had kept him from understanding their relationship previously.

[36] Therem Harth rem ir Estraven is a Gethenian from the Domain of Estre in Kerm Land, at the southern end of the Karhidish half of the continent.

In contrast to Estraven, he seems intent on starting a war with Orgoreyn over the Sinnoth Valley dispute; as well as taking aggressive actions at the border, he regularly makes belligerent speeches on the radio.

[43] Fellow science fiction writer Algis Budrys praised the novel as "a narrative so fully realized, so compellingly told, so masterfully executed".

[47] Darko Suvin, one of the first academics to study science fiction, wrote that Left Hand was the "most memorable novel of the year",[45] and Charlotte Spivack regards the book as having established Le Guin's status as a major science-fiction writer.

[7] In 1987 Harold Bloom described The Left Hand of Darkness as Le Guin's "finest work to date", and argued that critics have generally undervalued it.

[45] Suzanne Reid wrote that at the time the novel was written, Le Guin's ideas of androgyny were unique not only to science fiction, but to literature in general.

[51] In her responses, Le Guin admitted to failing to depict androgynes in stereotypically feminine roles, but said that she considered and decided against inventing gender-neutral pronouns, because they would mangle the language of the novel.

"[53] Le Guin's works set in the Hainish universe explore the idea of human expansion, a theme found in the future history novels of other science-fiction authors such as Isaac Asimov.

[22] The Hainish novels, such as The Dispossessed, Left Hand, and The Word for World Is Forest, also frequently explore the effects of differing social and political systems.

[26] Le Guin's later Hainish novels also challenge contemporary ideas about gender, ethnic differences, the value of ownership, and human beings' relationship to the natural world.

On Gethen, the permanently male Genly Ai is an oddity, and is seen as a "pervert" by the natives; according to reviewers, this is Le Guin's way of gently critiquing masculinity.

[17] The Handdarrata represent the Taoist sense of unity; believers try to find insight by reaching the "untrance", a balance between knowing and unknowing, and focusing and unfocusing.

Critics such as David Lake have found parallels between the Yomesh cult and Christianity, such as the presence of saints and angels, and the use of a dating system based on the death of the prophet.

His decision is an example of Le Guin's portrayal of loyalty and betrayal as complementary rather than contradictory, because in joining Gethen with the Ekumen, Ai was fulfilling the larger purpose that he shared with Estraven.

[25] A related theme that runs through Le Guin's work is that of being rooted or rootless in society, explored through the experiences of lone individuals on alien planets.

[59] According to University of West Georgia Professor Carrie B. McWhorter, shifgrethor can be defined simply as "a sense of honor and respect that provides the Gethenians with a way to save face in a time of crisis".

The soundest fact may fail or prevail in the style of its telling: like that singular organic jewel of our seas, which grows brighter as one woman wears it and, worn by another, dulls and goes to dust.

[12] The heterogeneous structure of the novel has been described as "distinctly post-modern", and was unusual for the time of its publication,[45] in marked contrast to (primarily male-authored) traditional science fiction, which was straightforward and linear.

[64] In 1999, literary scholar Donna White wrote that the unorthodox structure of the novel made it initially confusing to reviewers, before it was interpreted as an attempt to follow the trajectory of Ai's changing views.

[61] The narration is complemented by Le Guin's writing style, described by Bloom as "precise, dialectical—always evocative in its restrained pathos" which is "exquisitely fitted to her powers of invention".

[71][72] On April 12 and 19, 2015, BBC Radio 4 broadcast a two-part adaptation of the novel, starring Kobna Holdbrook-Smith as Genly Ai, Lesley Sharp as Estraven, Toby Jones as Argaven, Ruth Gemmell as Ashe, Louise Brealey as Tibe and Gaum, Stephen Critchlow as Shusgis, and David Acton as Obsle.