The Times: Holiday Su Doku 2: 200 Killer Su Doku Puzzles

Fans of Su Doku have an ever increasing desire for trickier puzzles and Killer Su Doku should satiate their appetites as it poses an even greater challenge than the Fiendish Su Doku puzzles. It takes the number placing puzzle to the next level by adding an element of arithmetic and one cannot rely on logic alone. The puzzles use the same 9x9 grid but there is a double test. The aim is not only to complete every row, column, and cube so that it contains the digits 1–9, the numbers within a second dotted-line grid have to add up to a specific total. Included are some Gentle and Moderate puzzles to serve as a warm-up but the emphasis is on the Tricky, Tough, and Deadly levels.