Citadel: The Concordant Sequence — Matthew S. Cox

Eleven year old Kiera Quinn is sure she's having a nightmare. She doesn't believe a nap that started in her suburban bedroom ends in an empty wasteland. She doesn't believe everyone she's ever known may have never existed―and she definitely doesn't believe an old man who tells her she will resurrect the world.The odd shaman clad in junk and old computer parts claims she is 'the child born of the earth,' humanity's only chance to survive. Desperate and scared, Kiera humors him, hoping her bad dream ends soon.Fate has a funny habit of getting in the way of destiny. New parents and a new home―even a super-primitive tribal village―feel like the best place for a child to be, not off saving the world. Adjusting to life without video games isn't easy, but her new mom and dad give her what her old ones couldn't: time and attention.Alas, Kiera's discovery of a secret within ancient ruins makes the ruler of the Citadel want to kill her. Her only chance is to hope a crazy old man wasn't so crazy―and that saving her parents won't destroy the whole planet.