Another is 'Giovanni's Room' by James Baldwin. While not strictly a typical science - fiction in the sense of having high - tech elements, it's set in a different cultural and social 'world' of sorts, dealing with themes of homosexuality and self - discovery. It's a beautifully written and thought - provoking book that has influenced many LGBTQ literature works in different genres.
A more recent one is 'The Long Way to a Small, Angry Planet' by Becky Chambers. It features a diverse cast of characters, including those who are LGBTQ. The story focuses on the crew of a spaceship on a long journey, and along the way, it delves into the relationships and identities of the characters in a very engaging way.