My favorite thing about science fiction is it is a lens through which to view possible futures and explore potential solutions. Salvation Day is an ambitious look toward the future after the Collapse forces humanity into space to find a new home. But beneath the surface, there is so much more to this story.
The world-building is vast; Wallace crafted a fully-realized future for humanity which touches on a refugee crisis, a government corrupted by power and secrets, and a group of people looking for a new home among the stars at any cost. There are multiple layers and motivations to this story, and it was exciting to see how everything connected.