Novel by author C.S. Friedman. Imagine a world where humanity had settled the stars - and then discovered the FTL travel that allowed it warped the colonists in horrible ways, creating new, viable subspecies of each set of colonists. Earth shuts down the colonization process, leaving the Variant survivors alone in the dark.

Jump many years into the future. FTL travel again exists, but only through the Guerans' Guild. Variants in the mind only, they have discovered the way to travel through wormholes called ainniqs inhabited by malevolent aliens called "dragons", and have reunited the original Terrans and the many different Variant races of the other human colonies. Earth corporations will do anything to break the hold on travel while many Variants despise those who abandoned them to survive alone. Both Terran and Variant supremicists look for a way over the other while the majority of humans simply live out their lives like always. Cut to a young teenaged girl in an Earth orbital under attack, and our story begins.

This is one of C.S. Friedman's better books. The future background of the book is interesting in and of itself, but the concept of the Guerans is amazing. Their Variant is the utter prevalence of full-blown mental disease in each and every citizen. Their society is based on the interplay between different syndromes. Considering that most mental illness is a magnification of otherwise normal behavior, the Guerans' methods of coping are very interesting. There's many other clever ideas and details thrown throughout the story, and the plot itself drags you along. Points for catching the blatant Cordwainer Smith reference mentioned in the introduction.