The Toughest Sudoku Puzzle Book:
200+ Puzzles to Sharpen Your Brain
by Cristina Smith & Rick Smith
Rockridge Press
5/19/2020
Activity Books/Puzzles
180 pages
Goodreads 

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People have different ways of relaxing. For some, after a tough day, they just want to watch an easy movie. For me, using my brain is actually the most enjoyable way of relaxing. After word games comes Sudoku. The Toughest Sudoku is definitely the best and most challenging collection I have ever found. Here is why.

Like me before I opened this book, you may think all sudokus are the same, beside the level of difficulty. Actually thanks to this book, I discovered  that there are many variations, with almost 20 kinds presented here!
I will just give here a couple of examples:
– Diagonal Sudoku: the two diagonals of the grid each also contain digits 1 through 9
– Kropki Sudoku, with cells separated by a black or a white circle. In the former case, one of the digits is twice the other. In the latter, the digits are consecutive. Cells without circles between them are neither double nor consecutive.

All these variations can still be solved with the same main techniques, that are very nicely explained in the first part of the book, with examples (Naked Pair, Swordfish, etc). 

So once you feel ready, you can start having fun.
And no, the book does not begin with easy Sudokus! The three levels are Tough, Tougher, and Tear-Your Hair-Out!
If you still have hair on after sudoku #190, you can try the Extra Credit section, with more crazy variation, like the Kropki explained above.

There are 240 Sudokus in total offered here by Cristina and Rick Smith, who are brother and sister.

Another clever element of the book is the Hint section. Most books I know just give you the answer key, and it’s always hard to just look at say, one line, to help you when you are stuck. So here, for each sudoku, you get a hint, telling you the number you should put in one square. If this is not enough, you can look further in the next two areas offering you 2 other hints. 

And if you are really desperate, the answer key is at the very end of the book.

VERDICT:  The most challenging sudoku book ever, but with brilliant explanations of techniques and variations. Sharpen your brain and have fun!

In full compliance with FTC Guidelines, I received this book free of charge from the publisher through The Callisto Publisher’s Club. I was in no way compensated for this post as a reviewer, and the thoughts are my own.