Even within LGBTQ speculative fiction, gender identity remains something of a fixed characteristic. You might see relationships between gay characters in science fiction, but rarely do you see examples of characters who don't fit neatly within the gender binary. Ursula K. Le Guin's novel The Left Hand of Darkness stands as the exception to this trend. Its story takes place on a planet called Winter, whose inhabitants live without gender identities. Only when they feel sexual urges--which is about once a month--does gender come in to play. The rest of the time, they live collectively without it. The possibilities of science fiction allow for so much of this kind of exploration of gender within society, and yet few authors take advantage of it. Props to Le Guin for exploring the territory.