When you buy this book you get an electronic version (PDF file) of the interior of this book. Killer Sudoku is a fun and addicting logic puzzle game that combines Sudoku with an addition math game. Killer Sudoku is a fun way for kids and adults to practice addition facts. This book is ideal if you already know how to solve Killer Sudoku puzzles but find our hard Killer Sudoku puzzles too difficult. Once you pick up this book, you won't be able to put it back down. You have been warned! The goal of Killer Sudoku is to fill in the empty cells, one number in each, so that each column, row, and region contains each number exactly once. The sum of all numbers in a cage (indicated by the dashed lines) must match the small number printed in its corner. No number can be repeated within a cage. Killer Sudoku 9x9 - Medium is a collection of 270 puzzles: 216 medium Killer Sudoku 9x9 puzzles 54 extra logic puzzles I guarantee that every logic puzzle in this Killer Sudoku 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 PuzzleBooks.net books. Killer Sudoku is also known as Sums Sudoku, Sumdoku, Sum Doku, Addoku, Killer Su Doku, Samunamupure, Kikagaku Nampure, Samu Nanpure, Sums Number Place.