I had heard about it on NPR, that it began in Japan and that it's taken the British Isles by storm. I knew that the Milwaukee Journal Sentinel had recently begun adding it to the daily puzzle offerings. But I hadn't really understood the maddening addictiveness of Sudoko until I actually tried the online version.
It's a logic puzzle. The puzzle is a square grid, containing nine nine-patch grids. You have to figure out the arrangment of the numbers: each ninepatch grid needs to contain the numbers 1 through 9, and each row of the puzzle, horizontally and vertically, must contain only 1 through 9 also. No math computation need be done. Just logic.