The Sudoku puzzles in this book are amongst the hardest, toughest and most difficult, advanced Sudoku puzzles published in any Sudoku book available. You will not find puzzles as challenging as these in ordinary Sudoku books or in newspapers such as the New-York Times, the NY Post or the Daily Telegraph. Even advanced Sudoku books claiming to contain hard, very hard, killer, devilish or fiendish Sudoku puzzles are often childsplay compared to the truly Extreme Sudoku puzzles found in this book.

To solve these Extreme Sudoku puzzles you will need to make use of a variety advanced Sudoku resolution techniques, sometimes in combination, for the most difficult puzzles.

As the use of pencilmarks is required for most of the more advanced Sudoku resolution techniques, pencilmarks are pre-computed and printed in half of the grids in this book, for your convenience.

The techniques or strategies that you might need to use to solve the puzzles in Extreme Sudoku include the following: