This Wretched Valley by Jenny Kiefer

Take only pictures. Leave only bones.

This trip is going to be Dylan’s big break. Her geologist friend Clay has discovered an untouched cliff face in the Kentucky wilderness, and she is going to be the first person to climb it. Together with Clay, his research assistant Sylvia, and Dylan’s boyfriend Luke, Dylan is going to document her achievement on Instagram and finally cement her place as the next rising star in rock climbing.
Seven months later, three bodies are discovered in the trees just off the highway. All are in various states of decay: one a stark, white skeleton; the second emptied of its organs; and the third a mutilated corpse with the tongue, eyes, ears, and fingers removed.
But Dylan is still missing—and no trace of her, dead or alive, has been discovered.

Were the climbers murdered? Did they succumb to cannibalism? Or are their impossible bodies the work of an even more sinister force?