I really like the book - I think it's one of his best. Subtle 'unreliable narrator' mind-fuck from beginning to end, nicely written and characterised. The film of it is an abomination, though.

Could be a tilt shift lens which can distort perspective and make a photo look as if it's being taken from a slightly different angle. Not sure what to look for to disprove that hypothesis though.

i noticed that in the OP too and it confused me a bit. then i noticed the dark corner bottom left, which is probably a bit of the wall of the dark room the picture was taken out of. that's why the photographer isn't in the reflection.