This is volume 4 of the acclaimed series of books with the most difficult Killer Sudoku puzzles. All puzzles in this volume are new, previously unpublished.
It contains only puzzles of the 3 hardest levels of difficulty: BRAIN, IQ and INSANE, with addition of a few puzzles of an even more fiendish kind - Zero Killer Sudokus.

Contents:
• 40 BRAIN (5 ZERO)
• 60 IQ (5 ZERO)
• 12 totally INSANE (6 ZERO INSANE)

For a total of 112 toughest Killer Sudoku puzzles
By no means is this a book for a novice Killer Sudoku solver. It is intended only for the most experienced and most persistent of those who are already masters at solving Sudokus with sums.
So... are you up for this challenge?