200 Sudoku Challenges - Testing Your Brain To Keep You Young - Hard Difficulty Volume 1. Book one of the Sudoku Puzzle Book Series. This Book Contains 200 Easy Sudoku Puzzles with answers, for Sudoku Puzzlers. Welcome to Sudoku Challenges, which provides you with 200 Sudoku puzzles to test your brain to keep you young. This volume gets you started into the fascinating and addictive world of Sudoku. You are joining a family of millions of people worldwide who enjoy challenging themselves everyday. At the start of the Sudoku Challenges puzzle book you will find a brief introduction to the rules of Sudoku if you don't already know them. When you get started on the puzzles you will see that at the top of each puzzle there is a difficulty rating - the higher the number the harder the Sudoku challenge. There are 4 sections of 'Hard' Sudoku challenges but at the end of the book there are 8 Sudoku challenges that we would describe as very hard difficulty. This is to get you in training and ready for the next book in our series. When you have completed a Sudoku challenge you will find the answers for each section at the end of the book - so you can check how well you have done....or give yourself a clue if you get stuck. Enjoy and good luck!