This image is very well composed and the only thing I would add to the image is to fill in numbers into the square that is captured inside the lens. This would really strengthen the relationship between the glasses and the puzzle.
On the technical side, all this needs is a little levels adjustment to make the paper whiter. My suggestion is set the Levels Inputs at 0 - 1 - 191 and then do a noise reduction.
I love Sudoku. I think the compression on this JPG image might be a little high though. I can see artifacting around the lines in the image - which I believe is due to the compression. I would have liked to have seen the image a little brighter as well.