Another perfect xmas present! Was gonna buy that on black friday lightning deals but this gotten even cheaper now! Retail price was £20+ so its pretty good deal.
About the book set:
Specially compiled to provide the most devilishly difficult challenge, Ultimate Killer Su Doku Books 1, 2 and 3 are for Su Doku enthusiasts who need puzzles to really test their mettle.
Prepare yourself for the toughest Su Doku challenge there is. These diabolically difficult Ultimate Killer Su Dokus will really put your brainpower to the test as you warm up with a selection of Deadly Killer puzzles before steeling yourself to take on the Extra Deadly Su Dokus. Are you ready for the challenge?
The Times Ultimate Killer Su Doku Books 1, 2 and 3 are not for the faint-hearted. The puzzles use the same 9x9 grid as a regular Su Doku, but have an extra mathematical element that makes them a real challenge. The aim is not only to complete every row, column and cube so that it contains the digits 1 to 9, but also to make sure that the outlined sections, called cages, add up to the number given in each cage.
Warning: Not suitable for amateur puzzlers.