NIN Ghosts Photos (dark edges and grainy?)

So below are examples of Rob Sheridans photographs that came with the Nine Inch Nails album, Ghosts. Now that I'm getting into photography, I decided to refer back to his work and noticed that almost all his photos
are grainy and have these large graduated dark edges.

Question time:
- is the grain in these photos "good"/intentional? (it looks like you can even see the very subtle "squares" where the grain patterns repeat, suggesting he intentionally added them in with photoshop; something...

NIN Ghosts Photos (dark edges and grainy?) NIN Ghosts Photos (dark edges and grainy?)