When it comes to boosting your focus, concentration and mental skills, Sudoku puzzles are exactly what you need. But just like all other puzzles, you need to find a real challenge that will push you to your limits and make the taste of solving the puzzle so much sweeter. Here are the requirements to even pick up our Sudoku puzzle book: : if you have snapped hundreds of pencils in half trying to find a number that solves the puzzles, then you are welcome. : if you have uttered this phrase more than 100+ times and lied to yourself every single time, then you are ready to start solving our puzzles. : if every time you close your eyes, all you can see is 9 rows, 9 columns and 81 cells, then you are our ideal candidate. Surprise your wife, husband, boyfriend, girlfriend, father, mother, sister, brother, grandparents or grandkids with our must-have Sudoku puzzle book!