The Times Killer Su Doku Book 13: 200 Lethal Su Doku PuzzlesPaperback, 1 August 2017

The puzzles here use the same 9x9 grid as Su Doku, but with an added mathematical challenge. The aim is not only to complete every row, column, and cube so that it contains the numbers 1-9--it is also necessary to ensure that the outlined cubes add up to the same number as well. With 200 new Moderate, Tricky, Tough, and Deadly Killer Su Doku puzzles, there is no chance to ease yourself in with simple puzzles.