The Sinister Secrets of Singe — Sean Ferrell

The Wild Robot meets Sweet Tooth in the first book in a sweeping adventure series packed with robots, smugglers, battles, and a lonely boy trying to find where he fits in the world.

Eleven-year-old Noah has grown up in a mysterious house that grows larger every night with only his mother and a robot-boy for company. He spends his days building robotic devices for the city of Liberty, a place he's not even allowed to visit -- not since his father almost destroyed it when Noah was only a baby.

When Noah discovers a message hidden in one of his father's inventions, he decides to run away to find him. He's sure that at his father's side he'll finally get the recognition he deserves. With the help of a band of smugglers (especially unofficial second in command, young Winona), he sails to Singe to rescue his father, who he's certain is as misunderstood as he is, but the man he finds there is even more  of a monster than his mechanical creations. And when Noah returns home, he accidentally leads his father's robot army to Liberty once more. 

Now, it's up to Noah to rescue the city -- but to do so, he'll have to make a terrible choice.