In the Horde's Way. After the Collapse, #3

When a new trooper starts working at the Southwest Library, she meets Alaya, the Librarian's daughter. But for Henrietta, a soldier with a secret, this young woman may hold the key to expelling the invaders. The events that follow launch Henrietta on a journey that is dangerous and epic, leading her into the councils of the invaders and chieftains of the tribes that rule the desert land of the Southwest.
But an even greater danger is coming. Something is moving into the land, something more evil even than the dominating ruling clans. Messengers warn of a mounted menace moving down from the north, destroying all in its path. Facing the rising threat, Henrietta must join with the librarians and old enemies to build a stronger alliance. In this tale of the future world without modern technology, each character must make decisions of loyalty and commitment that will shape the future.