If we had to find a single word to describe the stories of Manly Wade Wellman, it would be:

INSIDIOUS

Allowed two words, we might say: 

EARILY CHARMING

Three, and we could add:

HYPNOTIC, CHILLING, TENDER

(But that would leave out the humor)

Perhaps the hero himself describes the feeling of these stories most clearly when he says:

"...you'd best go expecting anything!"

Introduction to Manly Wade Wellman's Who Fears the Devil. 1963