I read this for the first contact category in my SF Reading Challenge.
Centuries after a nuclear war destroys civilization on Earth, the main character, Lilith Iyapo, awakes to discover that she is held captive aboard a starship. Her captors, the Oankali, have rescued the remaining humans and restored Earth. However, this rescue was not without a catch -- these hideously grotesque aliens survive by merging genetically with primitive peoples.
The basic question is if the surviving humans should "mate" with the aliens in order to continue a form of human species on Earth or let the human race die out through a "clean" death.
This book would also satisfy the non-caucasian category and probably social SF. The Oankali ship is multi-generational for their species although the humans are in suspended animation for most of their time on the ship.
This book is the first in the Xenogenesis series.