The Rock Jockeys // Devil's Wall — Gary Paulsen

The rock wall above them was as smooth as polished black marble. There were no crevices and no ledges. They would have to fight for every inch. Rick looked at his friends. J.D. and Spud nodded silently. Rick stood up and started. His job would be to make the trail. Their job was to make sure he lived through it.
 
High atop treacherous Devil's Wall, The Rock Jockeys find much to explore. Sheer mountain cliffs. Wild woodland. Even a crashed B-17 bomber! But when they stumble upon a crew member's diary -- and underneath other eerie clues -- the boys realize Devil's Wall also holds a gruesome secret. That secret leaves The Rock Jockeys with a haunting question: If trapped on the mountain, would they do anything it takes to survive?