Are diagonal corners concidered adjacent?
From the middle of the right-hand side of page 8 of the rulebook:

Quote:
Investigators may move between two spaces that are diagonally 
adjacent. Due to imperfections in die cutting, if spaces between 
two tiles appear that they should be diagonally adjacent, then they 
are. All non-adjacent spaces very clearly do not share a white 
border by at least 1/8 of an inch.