Hammerfall is the first volume of a new series. Set on a desert world, populated by tribal colonists, it depicts a struggle against the elements that has shaped a culture that was obviously once hi-tech and space-faring into one similar to the pre-Islamic Arab world. An epidemic of madness has led to the world's near-immortal ruler, the Ila, calling for the mad to be brought to the hub of the world - the city of Oburan. Marak Tais Tain is one of the mad - but he's also a failed rebel...
The madness is driving its sufferers east, out into the raw lands that have yet to be changed by the hand of man. The Ila sends Marak and a group of the mad out into the east to find the source of the madness' compelling call. It's a mission that will change the world completely, forcing an end to its isolation, and an accounting for the Ila's sins. But before that happens, Marak needs to save as many as he can before the Hammer falls from the sky.
Cherryh is telling a story of change. Changed worlds, through nanotech and terraforming, changed peoples, and changed ideas. Marak isn't a catalyst for change - he's one of those who changes the most. Instead, the changes are wrought by powerful presences, somewhere off stage. The Ila has raped a world, forcing change where none was needed, or (indeed) even permitted. Now she must pay the price, and it's the one-time rebel tribesman who must help build a new world from the shattered ruins of the old.
Hammerfall is an excellent story, and a very different direction for Cherryh. It will be interesting to see where she takes the rest of this new series: The Gene Wars.