Book excerpt: Everyone knows sudoku is enjoyable--but these addictive puzzles come in endless variations too! They range from simple to very difficult, and can take almost no time to finish...or require many hours. This entertaining collection showcases a wide range of possibilities, offering solvers who have become accustomed to the standard rules and grids an exciting new challenge. Select from Mega Sudokus that provide a real workout; Diagonals or Odd and Even versions with extra constraints; Sum Sudokus that merge with kakuro; and Multisudoku with overlapping puzzles. There's something for every level--12 x 12 puzzles, ones with irregularly shaped areas, even Mini Sudoku--and lots of fun for everyone.