In Mankind's expansion through the galaxy, one of its conquests was the inhabited planet of Sarnia. They ran the planet for about 40 years, until they were beaten by the Mi'ukmac. That was over 130 years ago.
Sarnia is a busy place. Before Mankind came, the planet was run by the Toharrians. Several plagues devastated the three indigenous species, leaving large areas of Sarnia's one continent uninhabited. After the Mi'ukmac took over the planet, they herded all humans into one small area on the eastern edge of the continent. Humans were presented with several good reasons why any attempt to expand their area of residence is a bad idea. Just to make things more complicated, the Mi'ukmac control Sarnia, but they don't administer it. They handed that to another race, the Nu'homish.
Years before, a human rebellion caused the Mi'ukmac to shut off all electric power to the humans, and they show no inclination to turn it back on. Society has therefore regressed to a pre-industrial level. A huge complication is the existence of flying predators (something like pterodactyls) that would love to devour an animal or person. That is why all human habitation, farms and towns, is covered by nets and cables strung from trees and poles. That is why there are no fields of grain (the soil is not good for Earth agriculture) or herds of animals in a pasture. Human houses consist of three levels: the top level is the greenhouse, where the agriculture happens; the middle level is the living quarters, and the ground level is where the animals are kept. The Mi'ukmac are also keeping away any new colonists from Earth.
Considering that this is the first of a projected nine-book series, the actual plot may be a little thin. But the author has done an excellent job at society-building. This is a thick book, but, yes, it's worth reading.