I like Sudoku as well, I've a couple of books that fit in my bag for when I travel, I have yet to try the really hard ones, doubt if I've got the brains to complete one.
sudokus great! really good for long haul flights. u can buy books fullof them at different ranges of difficultiness.
cures boredom and gets ya brain working.
love general knowledges quizzes too. pretty ace. xx