This book includes 200 Sudoku puzzles from hard to easy just like the title says. It was the first book that I made with specific keywords in mind. What I mean by that is a measurable amount of people type excactly the title into Amazon and look for it. So I tried to do a book to match excactly what someone would be looking for that types that in. Sudoku is a fun game. It's based on trying to isolate numbers so you know where the numbers are supposed to be placed in the puzzle. Because every line, row and a 3x3 square, can only have a single number included once from 1-9. If you love Sudoku this book is available on Amazon.