Relax and enjoy solving these 450 Hard and Very Difficult puzzles to stay sharp and have fun! This large-print 8.5" x 11" book won't fit in your pocket, but you can slip it in your briefcase, carry-on or beach bag and relax with a puzzle in your spare moments. You can also just tear out a page and take it with you.One big puzzles on each page give you plenty of space to note candidates and sturdy paper holds up well to erasing.Extra wide center margins make it easier to solve the puzzles when you fold the book back.Large print on white paper is very easy to read (even in dim light).Each puzzle has one solution - provided at the back of the book. Go ahead and peek if you get stuck or want to verify your answer.Advance from Hard to Very Difficult puzzles as you improve and gain experience.Get more than one book and arrange a friendly challenge!If you were misled by other books with trivial Sudoku puzzles labeled "difficult" or medium puzzles called "hard," we feel your frustration. What is "easy" for one person can be a serious challenge for another and categories are not precise. Because there is no official Sudoku grading standard, you have no way to compare puzzles from different authors. For example, a medium puzzle in one book can be called hard in a newspaper or in a book by a different author. We determine difficulty by the logic techniques needed to solve the puzzle. Look inside the book to see the logic techniques used for Hard Sudoku.