The ideal gift for sudoku enthusiasts.

If you enjoy living dangerously and pushing beyond your mental comfort zone, prepare for the toughest Ultimate Killer puzzles from The Times. A collection that includes over 360 puzzles, specifically for hardcore solvers. Selected by The Times, these puzzles will challenge the sharpest minds.

Included are Deadly-level Killer puzzles and Extra Deadly, which will truly test your limits: this is the only place where you'll find such a torturous collection in a single book.

These puzzles are not for the weak: they use the same 9x9 grid as Sudoku and have an additional mathematical challenge. The goal is not only to complete each row, column, and box so that they contain the numbers 1-9, but it is also necessary to ensure that the surrounding boxes add up to the same number.

But unlike previous books, there is no opportunity to warm up with Easy or even Tough puzzles: this book is the Ultimate Killer Su Doku – completely lethal.

The puzzles in this collection have been taken from the Times Ultimate Killer Su Doku books 5, 6, and 7. Pages: 448, Dimensions: 12.9x12.9cm.