Sudoku (Japanese: 数独, sūdoku), sometimes spelled Su Doku, is a logic based placement puzzle, also known as Number Place in the United States. The aim of the canonical puzzle is to enter a numerical digit from 1 through 9 in each cell of a 9×9 grid made up of 3×3 subgrids (called "regions"), starting with various digits given in some cells (the "givens").
I learned about Su Doku earlier in the year. I must have caught an article on it somewhere. At that time, it was very popular in Europe but still hadn’t made major inroads into the US. I wound up buying Jean a book of puzzles (Su Doku for Dummies I think), and then solving some of them myself! She was forced to get me my own puzzle book so that I’d stop solving hers. It’s a great way to pass some free time, and for her, during the day with the kids, its perfect.
Now, she’s far enough through the book that she’s into the really hard puzzles. I dunno when she’ll be done, but I wanted to mention that there are web-based alternatives, such as Websudoku. I prefer that site to the one on USA Today. I guess it’s a personally preference, but I like the ability to use pencil marks (under options) on Websudoku. This makes it more similar to the traditional approach.
I’d recommend reading the Wiki first and getting a good grasp on the game. It’s about logic, not about math. Understanding how the solve for unknown values from known values, or process of potential elimination.