From amazon.com:

One hundred years before Ender's Game, the aliens arrived on Earth with fire and death. Earth Afire by Orson Scott Card and Aaron Johnston is the story of the First Formic War. 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.

From amazon.com:

Nearly 100 years before the events of Orson Scott Card's best-selling novel Ender's Game, humans were just beginning to step off Earth and out into the Solar System. A thin web of ships in both asteroid belts; a few stations; a corporate settlement on Luna. No one had seen any sign of other space-faring races; everyone expected that First Contact, if it came, would happen in the future, in the empty reaches between the stars. Then a young navigator on a distant mining ship saw something moving too fast, heading directly for our sun.

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.

From amazon.com:

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.

El Cavador has other problems. Their systems are old and failing. The family is getting too big for the ship. There are claim-jumping corporate ships bringing Asteroid Belt tactics to the Kuiper Belt. Worrying about a distant object that might or might not be an alien ship seems...not important.

They're wrong. It's the most important thing that has happened to the human race in a million years. The first Formic War is about to begin.