More on Sudoku

I have a friend who is addicted to Sudoku.  Rather than earphones and an ipod, he is usually to be seen with a pencil (eraser on end of course) behind his ear and a pocket book in his hand.

(Does a pocket book become a hand book if it's in your hand and does a handbook become a pocket book in the opposite circumstances? )

His wife has become a Sudoku widow. Once when I called I asked what her husband was up to.  "Oh, he's  into Sod You as usual" came the reply!