Freedom's Ransom by Anne McCaffrey (Catteni #4)

Used; Hardcover - like new; 1st printing, 1st edition; some minor wear of the dust jacket. 

When Kris Bjornsen and her fellow slaves were dumped on an uninhabited planet by the alien Catteni overlords, they would surely have died-without the help of Zainal, a renegade Catteni exiled by his own people. But they did survive on the planet they named Botany, and in time they drove the Catteni away from Earth and neighboring planets.

Technologically limited but rich in natural resources, Botany must find its place in the newly configured universe. A trip to Earth shows Kris and Zainal how desperately the devastated home planet needs what Botany can give. Other worlds too have had their wealth skimmed by the Catteni regime; the nearby planet of Barevi is little more than a corrupt bazaar, where bits and pieces of Earth's once powerful technology can be traded for with grain and mineral ores. Earth needs food. Botany needs technology-and, some say, the will to protect itself from being overrun by refugees. As alien influence fades, the people of Botany must decide what kind of world they will become.