This book has 250 of the popular Killer Sudoku puzzles, ranging from easy to very challenging. There are five categories: "Warmup" (with 25 puzzles), "Easy" (50), "Medium" (50), "Tricky" (50), and "Difficult" (75) (so no puzzle is actually impossible: -). Solving a Killer Sudoku takes a combination of Sudoku-style logic reasoning and basic math skills, making it a much more interesting puzzle. The puzzles are by the author of the popular Calcudoku puzzle books. Solve both Calcudoku and Killer Sudoku puzzles online at calcudoku.org and score points! You can even submit solutions for the difficult puzzles in this book, and score points for each correct solution. This 2nd edition has all solutions in the back.
When I heard I had won this book I was looking forward to starting the challenge. I had had another book with these types of Sudoku's in and I found them more fun and interesting than the typical Sudoku's.
I like how the Sudoku's are separated in chapters of difficulty as it makes it easy to find one you feel like doing at the time. Sometimes I don't feel like doing an impossible one which does seem to be impossible but I am still trying. It is good that there is a good amount of each difficulty so there will be puzzles to keep me going for a long time in the future.
I think the book is nicely laid out and it is handy to have some blank space around the outside of the grid for any notes that may be helpful.
The answers at the back are useful but I have not used them, I tend to think if it fits in it must be right, if not I have a problem.
I think these Sudoku's are great for a challenging puzzle and although they are tricky they can be done, I have let some of my family have a go at a few but they couldn't do it and didn't persevere to the end. I still have lots left to keep me busy.