The ultimate Sudoku challenge - Nikoli Nikoli

Sudoku is the simple number puzzle that has swept the world and obsessed millions of puzzlers of all ages. Test your IQ with 200 of the most fiendishly difficult sudokus ever devised. These puzzles - created by hand in Japan - have been designed to examine the sharpest minds and most competent puzzlers with absorbing grids that will give you hours of head-scratching enjoyment. Following on from the successful "Sudoku Challenge" this is the ideal book for Sudoku-ists everywhere! This pocket-book format means that you can work on a Sudoku anywhere - whilst commuting, on the beach, or during a lunch break. It includes mega sudokus on a 25 X 25 grid!