Nice Dragons Finish Last by Rachel Aaron

As the smallest dragon in the Heartstriker clan, Julius survives by a simple code: keep quiet, don’t cause trouble, and stay out of the way of bigger dragons. But this meek behavior doesn’t fly in a family of ambitious magical predators, and his mother, Bethesda the Heartstriker, has finally reached the end of her patience.

Now, sealed in human form and banished to the DFZ–a vertical metropolis built on the ruins of Old Detroit–Julius has one month to prove that he can be a ruthless dragon or kiss his true shape goodbye forever. But in a city of modern mages and vengeful spirits where dragons are considered monsters to be exterminated, he’s going to need some serious help to survive this test.

He only hopes humans are more trustworthy than dragons…