Worldshaker

Sixteen-year-old Col Porpentine is being groomed as the next Commander of Worldshaker, a juggernaut where elite families live on the upper decks while the Filthies toil below, but when he meets Riff, a Filthy girl on the run, he discovers how ignorant he is of his home and its residents.
Abstract: Sixteen-year-old Col Porpentine is being groomed as the next Commander of Worldshaker, a juggernaut where elite families live on the upper decks while the Filthies toil below, but when he meets Riff, a Filthy girl on the run, he discovers how ignorant he is of his home and its residents