Consider Phlebas (Culture, #1)

by Iain M. Banks

Good grief, the fascination of sex. No doubt it was great fun, but then how could people take it so seriously? Sometimes she felt a sneaking envy for the Idirans; they got over it; after a while it no longer mattered. They were dual hermaphrodites, each half of the couple impregnating the other, and each usually bearing twins. After one or occasionally two pregnancies—and weanings—they changed from their fertile breeder stage to become warriors. Opinion was divided on whether they increased in intelligence or just underwent a personality alteration. Certainly they became more cunning but less open-minded, more logical but less imaginative, more ruthless, less compassionate. They grew by another meter; their weight almost doubled; their keratinous covering became thicker and harder; their muscles increased in bulk and density; and their internal organs altered to accommodate these power-increasing changes. At the same time, their bodies absorbed their reproductive organs, and they became sexless. All very linear, symmetrical and tidy, compared to the Culture’s pick-your-own approach.

Fascinating