This collection investigates the limits of deductive reasoning through a series of high-difficulty numerical grid puzzles. Wayne Gould, the retired judge credited with popularizing Sudoku in the Western world, utilizes his expertise in logic-based game design to curate a set of 200 puzzles specifically calibrated for advanced solvers. The book operates on the premise that complex grid patterns can be resolved entirely through systematic elimination and logical inference without the need for mathematical calculation or trial-and-error guessing.

This volume is regarded as a standard reference for enthusiasts seeking to test their proficiency against the highest difficulty tier of the format. The inclusion of puzzles by the individual who introduced the game to the British press ensures a high level of technical consistency and adherence to the rules of logic.