I have not bought this but in the absence on info on Amazon.co.uk I was forced to find out for myself. I know it is another book by Wayne Gould and it is "Grand Master Su Doku Ultimate". Ultimate suggests it is either highest quality, or utmost or extreme, or the last of a series. Grand Master suggests only a few people are capable of solving these puzzles. It sounded very promising.
So I tried the puzzle on the cover. Not very difficult. If that puzzle is representative at all it is pitched somewhere below Fiendish.
I found some information elsewhere which says it is a collection of 150 unpublished puzzles of all levels, together with 5 Super Dokus (?), extra fiendish puzzles, and junior puzzles for children, is "Dokulicious". Hints and tips for solving the puzzles faster are provided. The ultimate treat for the Su Doku fan from the Grand Master of the game.
It is bit difficult to imagine who it is aimed at. I guess the concept is that it will be left on a table and anyone can pick it up and do a puzzle whether they are experts or children. It is not what I was hoping for so will not be buying it. I am forced to give a star rating even though this is not a review in the usual sense. However, I thought it useful to share my findings.