When you buy this book you get an electronic version (PDF file) of the interior of this book. CalcuDoku is a fun and addicting logic puzzle game that combines Sudoku with math. CalcuDoku is a fun way for kids and adults to practice addition, subtraction, multiplication, and division facts. This book is ideal for you if you love to solve difficult CalcuDoku puzzles no matter their size. You do not need to wade through tons of easy CalcuDoku puzzles before getting to the real brain teasers. You will experience extremely difficult CalcuDoku 7x7, CalcuDoku 8x8 and CalcuDoku 9x9. You get the perfect mix of different sizes of CalcuDoku to keep you entertained for weeks. Once you pick up this book, you won't be able to put it back down. You have been warned! CalcuDoku Mixed Grids Deluxe - Hard is a collection of 468 puzzles: 136 hard CalcuDoku 7x7 puzzles 136 hard CalcuDoku 8x8 puzzles 136 hard CalcuDoku 9x9 puzzles 60 extra logic puzzles I guarantee that every logic puzzle in this CalcuDoku puzzle book has been carefully checked to ensure that each puzzle has only 1 solution. None of the puzzles in this book will appear in any of the other English PuzzleBooks.net books. CalcuDoku is also known as Square Wisdom, CanCan, MinuPlu, Mathdoku and Calcu-Doku.