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,

The story of The First Formic War continues in Earth Awakens.
Nearly 100 years before the events of Orson Scott Card's bestselling 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