The ideal gift for su doku enthusiasts.If you like to live dangerously and push beyond your mental comfort zone, steel yourself for The Times'' toughest Ultimate Killer puzzles. A bumper collection of more than 360 puzzles for hard-core solvers. Selected from The Times these puzzles will challenge the sharpest minds.Includes Deadly-level Killer puzzles, and Extra Deadly, to really test your limits: this is the only place you''ll find such a torturous collection in a single book.These puzzles are not for the fainthearted, they use the same 9x9 grid as Su Doku, and have an added mathematical challenge. The aim is not only to complete every row, column and cube so that it contains the digits 1-9, it is also necessary to ensure that the outlined cubes add up to the same number as well.But unlike with previous books, there is no chance to ease yourself in with Easy, or even Tough puzzles: this book is the Ultimate Killer Su Doku – completely deadly.Puzzles in this collection are taken from Times Ultimate Killer Su Doku Books 1, 2 and 3.