Another 201 Puzzles, 5 Seriously Advanced Levels of Difficulty! The incredible popularity of Su Doku shows no sign of slowing and for every fan of the fascinating number game, The Essential Book of Su Doku Volume 3: Advanced will provide further hours of captivating fun — with the most challenging puzzles yet. The super-difficult puzzles created especially for this book will tax even the most agile Su Doku brains and leave people begging for mercy. Fiendishly devised for maximum fun, these puzzles are certain to take your Su Doku skills to new heights.