Ghost Heart by Weston Ochse & Yvonne Navarro

Trade paperback format. 

While Matt Cady's parents are contemplating divorce, Regina Running Deer can't grow up fast enough. Together, along with two dead-biker guardian spirits and an immense German Shepherd, they escape to the Black Hills. Steeped in bloody history, the Black Hills is a shadowy world where creatures, real and unreal, would rather see them dead than alive. Finally the cryptic advice of a witch, a fortune teller and a troll, plus the ghosts of Wild Bill Hickok leads them to find the very thing they didn't know they were looking for. And to get it, the must enter the Badlands...and survive.

"...this reminded me of the early Dark Tower books by Stephen King, although with a darker coloration." - Don D'Ammassa, Critical Mass