Floating boy and the girl who couldn't fly

"Things Mary doesn't want to fall into: the river, high school, her mother's life. Things Mary does kind of want to fall into: love, the sky. This is the story of a girl who sees a boy float away one fine day. This is the story of the girl who reaches up for that boy with her hand and with her heart. This is the story of a girl who takes on the army to save a town, who goes toe-to-toe with a mad scientist, who has to fight a plague to save her family. This is the story of a girl who would give anything to get to babysit her baby brother one more time. If she could just find him. It's all up in the air for now, though, and falling fast"--