The World Menders

From the back cover of the DAW first printing: "On the world Branoff IV live the RASCZ, an artistic superbly civilized race. Few of them are aware that their prosperous civilization is totally dependent upon the OLZ, a race of slaves owned by their god-emperor. The OLZ till the fields and work the forests and mines, and their reward is starvation and the whip. Cultural Survey trainee Cedd Farrari receives a routine assignment to Interplanetary Relations Bureau headquarters on Branoff IV. His delight with the culture of the RASCZ is shattered when he becomes aware of the horrible plight of the OLZ. He dedicates himself to their liberation, and to achieve that he must become one of them - must share their body-destroying labor and their starvation and torture. As he pursues his quest he finds himself leading the OLZ in the strangest rebellion ever described in truth or fiction: the RASCZ, the master race, doesn't know their slaves are rebelling. Neither do the slaves!"