Best fitness for the brain.100 puzzles Sudoku Calcudoku 9x9 - Very hard Levels. 100 puzzles Kakuro - 9x9 + 10x10 + 11x11 and 12x12 puzzles.100 puzzles Jigsaw Killer Sudoku - Very hard levels. 100 puzzles Tridoku Sudoku 9x9 - 25 Very hard levels. - unique puzzles+ 250 sudoku difficult level that can be downloaded and printed.+ 250 maze puzzles that can be downloaded and printed.- only 1 verified solution- all answers are at the end of the book- exclusive puzzles- a link to the surprise is at the end of the bookAn excellent book for free time and mind exploration.I hope you enjoy the book.Best regards, Basford Holmes