Beware: The Times Killer Su Doku gets about as close as possible to the label 'unputdownable'. In Book 2, the challenge continues with the emphasis on the tougher and more deadly puzzles. Prepare to be rattled. Killer Su Doku takes the number placing puzzle to the next level by adding an element of arithmetic. One cannot rely on logic alone. The puzzle uses 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. The word 'fiendish' doesn't even come close!