GNOME Sudoku

Play the popular Japanese logic game. GNOME Sudoku is a must-install for
Sudoku lovers, with a simple, unobtrusive interface that makes playing
Sudoku fun for players of any skill level.

Each game is assigned a difficulty similar to those given by newspapers
and websites, so your game will be as easy or as difficult as you want it
to be.

If you like to play on paper, you can print games out. You can choose how
many games you want to print per page and what difficulty of games you
want to print: as a result, GNOME Sudoku can act a renewable Sudoku book
for you.