Sick and tired of other Sudoku puzzle books claiming to be "Hard" or "Extreme" difficulty but they turn out to be medium at best? Your search for a challenging Sudoku logic brain teaser experience is finally over. Every single puzzle is selected and tested for their difficulty levels rather than being generated in mass production and carelessly cut and pasted like most others make. The puzzle on the cover is intended to be a sample of the difficulty found within with the solution on the back cover. The puzzle is one of the last most difficult puzzles. See how you like it. These puzzles are not for the feint of heart but they will take you far from your comfort zone so you can drastically improve your solving skills. Features: 144 Extreme difficulty level 9x9 puzzles with the solutions included in the back. Even though all the puzzles are Extreme you'll find that the puzzles at the start of the book are less extreme than the ones in the middle to the end. The final puzzle is the most difficult. Making a single book takes a lot of time because of the individual testing so reviews and popularity will determine if more are made. Premium glossy cover. 5x8 book size. Check out our line up of blank sudoku grid books which are great for practicing new solving techniques, copying your favorite puzzles or sharing with friends. This is the perfect gift for anyone serious about Sudoku.