From amazon.com:
From #1 New York Times bestselling author Brandon Sanderson: his debut novel for the young adult audience
More than anything, Joel wants to be a Rithmatist. Chosen by the Master in a mysterious inception ceremony, Rithmatists have the power to infuse life into two-dimensional figures known as Chalklings. Rithmatists are humanity's only defense against the Wild Chalklings—merciless creatures that leave mangled corpses in their wake. Having nearly overrun the territory of Nebrask, the Wild Chalklings now threaten all of the American Isles.
As the son of a lowly chalkmaker at Armedius Academy, Joel can only watch as Rithmatist students study the magical art that he would do anything to practice. Then students start disappearing—kidnapped from their rooms at night, leaving trails of blood. Assigned to help the professor who is investigating the crimes, Joel and his friend Melody find themselves on the trail of an unexpected discovery—one that will change Rithmatics—and their world—forever.
Bestselling author Brandon Sanderson brings his unique brand of epic storytelling to the teen audience with an engrossing tale of danger and suspense—the first of a series. With his trademark skills in world-building, Sanderson has created a magic system that is so inventive and detailed that that readers who appreciate games of strategy and tactics just may want to bring Rithmatics to life in our world.
A Kirkus Reviews Best Book of 2013 A New York Times Book Review Notable Children's Book of 2013