I thought this book was perfect. Hard and challenging, but not impossible. It was just right! I love that he does NOT use trialing for the results... only puzzle techniques. I have finished both of his books, and can't wait until he does another. It's my all-time favorite!

The small size of the numbers in the already filled in squares is annoying, if you are used to a different format. I got over this after about ten puzzles.
Make sure you read the notes in the forward about "trailing" and if you think that puzzles which involve what they call trailing are illegit, note the list of those puzzles, which allows you to steer clear of them.
It's smart to have blank grids at the back...sometimes it is great to start over clean!
These are hard...harder than the last book I did which was Japanese and supposed to be the hardest possible!

This book is excellent for the person who can do a medium to hard puzzle in minutes, not for a beginner at all. Do not be fooled by the instructions in the front, it will not help you at this level of sudoku.

This book was a challenge to me which is why I loved it so much! I developed my own techniques to conquer the puzzle. Mentally, a real workout.
Now, the only problem is I am having trouble finding another book like it, with advanced puzzles to challenge me. I need Sudoku Genius II.

Very Challenging - I loved this book so much, I ordered a second one when I was done with the first - I figured they were challenging enough to do it a 2nd time! I also ordered the second one in this series by Tom Sheldon.

I get a bit tired of people claiming how fantastically hard their puzzles are, only to be disappointed in the end. In the end with this book I was very disappointed. The author claims 9 Circles of Sudoku Hell, but the highest level, "The Ninth Circle" contains only one puzzle and it can be solved in under an hour, pretty much ditto for all the rest.

I thought the master class in advanced strategies disappointing, simply a rehash of strategies known around the world.

What I really came away with from this book is the knowledge that my Sudoku solving process is superior to the author's lore, and that maybe I should write a book on Sudoku solving and get the author's permission to use puzzles from this book as examples.