Orson Scott Card & Aaron Johnston – The First Formic War

A hundred years before Ender's Game, humans thought they were alone in the galaxy. Humanity was slowly making their way out from Earth to the planets and asteroids of the Solar System, exploring and mining and founding colonies.
The mining ship El Cavador is far out from Earth, in the deeps of the Kuiper Belt, beyond Pluto. Other mining ships, and the families that live on them, are few and far between this far out. So when El Cavador's telescopes pick up a fast-moving object coming in-system, it's hard to know what to make of it. It's massive and moving at a significant fraction of the speed of light.

Victor Delgado beat the alien ship to Earth, but just barely. Not soon enough to convince skeptical governments that there was a threat. They didn't believe that until space stations and ships and colonies went up in sudden flame.
And when that happened, only Mazer Rackham and the Mobile Operations Police could move fast enough to meet the threat.

When the alien ship screamed through the solar system, it disrupted communications between the far-flung human mining ships and supply stations, and between them and Earth. So Earth and Luna were unaware that they had been invaded until the ship pulled into Earth orbit, and began landing terra-forming crews in China. Politics and pride slowed the response on Earth, and on Luna, corporate power struggles seemed more urgent than distant deaths. But there are a few men and women who see that if Earth doesn't wake up and pull together, the planet could be lost.