Free sample from Extreme Sudoku 2: step-by-step solution
Print the puzzle first (PDF, A4 or US Letter), then come back and step through the solution, or skip to the hard parts.
Blue digits are placed by the walkthrough. Red strike-through marks a candidate being ruled out. Cells are named by row and column: R3C5 is row 3, column 5. Arrow keys step too.
The key technique: XY-Chain
A chain of two-candidate cells, each linked to the next. Whichever way the start cell goes, one end of the chain holds the digit, so cells seeing both ends cannot.
Every move above the basics is explained on the sudoku techniques page. The book's own 150 puzzles each have a page like this one: all Extreme Sudoku 2 solutions.
The book
Volume two: 150 new classic 9×9 grids, none repeated from book 1, ramping from hard to brutal.
Try a free sample puzzle (PDF) · prints on A4 or US Letter