Witch Bone (In the Pines Book 2). In the Pines, #2

Sometimes magic is simple-coffee grounds and salt, red pepper and castor oil. An old pair of glasses, a new deck of cards, a snippet of hair and the whisper of a crow's wing. Other times, it's far harder-mountain stone and a dead man's fingers, things that look human and demand a secret in payment, old trains that run only when the moon is dark and the creek is dry to carry you into the dark. It's been months since Silas Crane first encountered Eli, the shadowy Fetch with a goal in common: Find the man who stole away Danny, Silas' baby brother.
Find the man who has been stealing immortality from people like Silas, like Eli, people with their roots sunk deep in the old ways. Now, something else has stirred in the mountains. Something rides the darkness with Jackdaw and threatens to tear apart Silas' reality before they can find Danny, before they can stop this ancient thing creeping down the valleys towards the holler. Simple magics might be best, but the harder ones are sometimes more necessary.