Extremely challenging Sudoku puzzle books, not recommended for first-timers.nShare the fun with friends, colleagues, family and anyone who is interested in Sudoku books.nSudoku puzzles are the perfect gift for those who like the challenge. The complexity of the puzzles have been proven to form new connections in the brain.nThis bundle is composed of two books of Sudoku extreme puzzles. If itu0026#39;s too much for you to handle have some fun and get some help from a friend!nUse these Sudoku Hard Puzzle Books to relieve your stress. Whether you are at home, in the office or on the road traveling.nIf you feel like you've already mastered the easy and intermediate levels of Sudoku puzzles, then it's time to move on to the next level. Constantly challenging yourself will motivate and push you to do better. You can work on these Sudoku puzzles books on your own or you can get a little competitive by playing against the clock or a competitor. How will you choose to play?