The Product Features describe this product quite accurately, but they do not quite get over how much there is in this product. I have been doing Sudoku since day 1, and am constantly looking for more challenges. This is the one. This is a brilliant product. If you only have one Sudoku game make it this. There are rewards for completing various grids. These come in varying forms ie different challenges (grid based games, like subtract numbers to leave zero, joining pairs without lines crossing or shuffling numbers round to become sequential)or new skins or different fonts. If your stuck, you get clues,(so why not try a harder version occasionally?). There is an option for the easiest square on the grid.
This really is fantastic value. I bought it to last a fortnight on holiday including 2x 8 hour plane flights, and have used it constantly and haven't even won my way through to the 2 million grid option yet. I have even started playing Kakuro following the very informative inbuilt tutorial.
I read all the other Amazon feedbacks for other Sudoku and was sceptical about spending so much money, but I can honestly say this is real value for money.