Only Human — Sylvain Neuvel

Brilliant scientist Rose Franklin has devoted her adult life to solving the mystery she accidentally stumbled upon as a child: a huge metal hand buried beneath the ground outside Deadwood, South Dakota. The discovery set in motion a cataclysmic chain of events with geopolitical ramifications. Rose and the Earth Defense Corps raced to master the enigmatic technology, as giant robots suddenly descended on Earth's most populous cities, killing one hundred million people in the process. Though Rose and her team were able to fend off the attack, their victory was short-lived. The mysterious invaders retreated, disappearing from the shattered planet ... but they took the scientist and her crew with them.

Now, after nearly ten years on another world, Rose returns to find a devastating new war -- this time between humans. America and Russia are locked in combat, fighting to fill the power vacuum left behind after the invasion. Families are torn apart, friends become bitter enemies, and countries collapse in the wake of the battling superpowers. It appears the aliens left behind their titanic death machines so humankind will obliterate itself. Rose is determined to find a solution, whatever it takes. But will she become a pawn in a doomsday game no one can win?