The Nebula Tales - The Nebula Tales

The Nebula Tales consists of three novels - Thirds, Thirds Rising, and Thirds Aflame, to be read in that order. As humankind expands across and explores the Galaxy, they reach the Orion Nebula, the most famous of star factories, where they encounter a humanoid space-faring society - Surana. The Suranans, though humanoid, are different: they are tri-sexual - three genders participate in procreation.
Like humans, the Suranans have males and females, but there is a third gender - tris, or "Thirds" - which are sterile hermaphrodites exerting a powerful effect on procreation among Suranans. The three genders are very different. Tris are smaller and weaker, and many believe they are less intelligent. On Surana tris are second-class citizens, denied many of the benefits of that society. The physical and psychological differences result in widespread abuse and discrimination against tris, whose lives are usually brutal, miserable, and short.
But the tris have their own sources of strength and resourcefulness. The day comes when the tris rebel against the other Suranans, and civil war rages across Surana with the heat and power of a forest fire. The war begins with physical violence, but the conflict moves into other arenas - politics and biology. Science becomes a weapon. And when the war has gone on for months, when a mountain of wealth has been expended and thousands of lives lost, a human and a tri engage in an act as small, mundane, and normal as any act could be.
And yet, that small act - that littlest of little things - exerts a stupendous effect on Suranan politics, extinguishes the conflict, and completely undermines the motives to continue the war.