Waking Gods (Themis Files #2) by Sylvain Neuvel
In her childhood, Rose Franklin happened to make an extraordinary discover; a giant metallic hand that was buried within the earth. From that time, she embarked on finding answers as to what led to the events. She dedicated her entire adulthood to the investigation, producing astonishing answers as well as perplexing questions. When the truth is closer, another robot, more massive than the first one begins unleashing a deadly force on the humankind. They think they can turn the tide if only they unlock the mystery of an advanced alien technology.