Absolutely Nasty Kakuro Level Three: Dangerously Difficult Number Puzzles by Conceptis Puzzles (Paperback, 2013)

This is the third level of this puzzling series. This handy spiralbound format can be laid flat. Only hardcore kakuro devotees should dare enter here. For those who can, it's head-exploding puzzle solving. Kakuro is a puzzle type in which sums are given and solvers must deduce the numbers in the individual boxes.