While Charlie Manx looks at his map, several of the locations seen on the map are connected to works by both Joe Hill himself and Hill's father, Stephen King.
Derry, Maine, is marked as "Pennywise Circus". Derry, Maine is the setting of Stephen King's "IT". Pennywise and Manx both like to steal children using seemingly innocent ideas turned deadly (clowns, and Christmas respectively). And both exist in places where reality is thin.
"The treehouse of the mind", is also featured in Joe Hill's second published novel "Horns", and according to Hill himself is both an inscape and also a means to access the inscape, much like the Wraith in NOS4A2.
"Lovecraft keyhole", probably refers to Joe Hill's comic book "Locke & Key", which takes place in the fictional town of Lovecraft, and where keys and keyholes play a significant role.
