Wolfbane by Frederik Pohl
The Earth has been torn away from the Sun, kidnapped by a runaway planet , whose inhabitants - enigmatic, utterly alien Pyramids - have their own plans for Earth's resources. And humankind, depending for warmth on a constantly renewed but woefully inadequate Moon, wracked by hunger and ruled by a slavish conformity to tradition, is dying out. But there are those who defy convention and refuse to give in. Feared and persecuted by the ordinary citizens, these 'Wolves' are preparing to fight back against the Pyramids.