I like SF/fantasy stories that feature gay or queer elements but don't treat it as a big deal and wait to reveal it so it's a pleasant surprise. Examples (SPOILERS):

*2312 by KSR: You find out like halfway through the book that the main character, a woman, has a penis and used to be a man. She eventually winds up having sex with another character, a man, and they have two penises and two vaginas between them, so they're able to fuck each other at the same time.

*The Fifth Season: The book plods along for a couple hundred pages and then suddenly it's all like BAM! here's an MMF triad with two of the main characters, and explicit gay buttsecks

Probably some others but i can't think of them. In SF, authors tend to use the "in the future gay sex is ok" trope but don't actually deliver with any man on man action, if there's homosexuality it's between women. For all his genius, Iain Banks is the worst offender I know of, save for ONE scene in the entire culture cycle in which a man whose body is covered in penises is getting them all jerked off by a group of men and women.