Author: The Times Mind Games
Sudoku & number puzzles 
Published 03/05/2018 by HarperCollins Publishers (Times Books) in the United Kingdom as part of The Times Su Doku series 
Paperback | 272 pages
Challenge yourself at home with word and number puzzles
 These are previously unpublished quality Su Doku grids from the puzzle providers to The Times, and help to develop you to take on Extreme Su Doku.
 The 200 puzzles in this collection of treacherously difficult puzzles will stretch even the most advanced Su Doku enthusiast. You will need to use all of your best solving techniques to get to the end of this testing challenge.
 The puzzles in the collection are of the highest quality and are perfect for the advanced solver in need of a constant supply of ultra-difficult puzzles.
 Guaranteed to provide hours of mind-stretching entertainment.