In Volume 4 of Professor Puzzleworth's Hard Sudoku, the good professor has gathered together 100 of his favorite mind-boggling hard Sudoku puzzles for you to solve and enjoy. As you make your way through this collection, the professor will put your mind to the test as you search for a solution to each of these perplexing Sudoku puzzles. With page after Sudoku-filled page, this premium collection of puzzles is sure to provide you with hours of entertainment. So, if you think you have what it takes to match wits with Professor Puzzleworth, get ready to get solving as you put your skills to the test with this incredibly entertaining collection of hard Sudoku puzzles.