From New York Times bestseller and master of speculative fiction Garth Nix comes his first foray into adult science fiction with a brilliant and poignant story of sentient starships, galactic warfare, and the bonds a crew forms in the cold, black of space.

They are called Massifs and they have changed the course of humanity forever.

Before their arrival, Earth was on the verge of collapse. The population was too high, resources too low, and war dominated the globe. But then a Massif appeared: a giant, spacefaring vessel made of rock, customized for people to live on, populated by strange creatures and a single avatar, a visual manifestation of the sentient being that controlled the ship.

Communication was surface-level at best, but the message was clear: come aboard and I'll take you to the stars.

Soon the world was united and there were a number of Massifs shooting in every direction from Earth. Planets were being colonized, food and water was plentiful, and humanity seemed on the verge of a golden age.
However, not everything was so benign. War - humanity's curse - erupted between Mars and Earth as they competed for control of the Massifs. But the Massifs abhorred violence - to the point of forbidding any kind of fighting on their surfaces, often with brutal violence of their own. And there were mysteries that still refused to be solved, including how to speak to the avatars . . . and why some people were more sensitive to the energy fields the Massifs gave off.

But what has been hidden will soon be revealed when the crew of a smaller vessel loses one of their own, stranded on a planet, when their ship is incapacitated. They need the Massif to provide them with a new spacecraft . . . and that means figuring out how to talk to it. When they do, though, they are not prepared for what they learn . . . and how it might affect humans and the rest of the galaxy forever.