Inkling by Kenneth Oppel

Mishaps and madness ensue when magical drawing ink comes to life in the Rylance home and 11-year-old Ethan tries to prove he's just as talented as his famous father.A moving but light-hearted story about grief, family and a sixth-grade rivalry. When Ethan's class is given the task of creating a graphic novel and magical ink jumps out of his father's sketchbook, a strange series of events is set into motion. To his younger sister, Inkling is Lucy, her beloved dog; to his father, Inkling is a second chance at a dwindling career and a chance to solve his family's money worries. Friends and enemies alike try to use Inkling to ace tests and create bestselling comic books, but to Ethan, Inkling is his friend – and he must do everything in his power save him.