Long recognized as a great "puzzler," not just for sudoku but for his NYTimes crosswords, Will Shortz provides 400 puzzles of difficulties ranging from "Light and Easy" to "Beware! Very Challenging!" Regardless of the level, these puzzles are scrupulously fair, requiring, in my experience, only two occasions of "trailing" (and those may have been my own fault), when most other such books often require the puzzler to use this "technique" many times during the book.
"Trailing" is the controversial "technique" in which a puzzler, unable to move further in the puzzle, (desperately) chooses a number from a set of pairs and inserts it into the box. The puzzler then trails the results as they suggest other solutions involving other numbers throughout the puzzle to see if they work or if, eventually, you get duplicates in rows, columns or squares. (If you do, you have to backtrack and insert the other number from the pair, which should work.) Many puzzlers feel that this "technique" is not "logic" but guesswork.
The book is a convenient size and has a spiral binding. The puzzles are large, and the pages are smooth and very white, allowing you to write in plenty of options and do whatever erasing you may require without roughing up the surface of the page (in case you decide to start over). Some of the puzzles which look the most difficult and have the most empty spaces are, in fact, the most fun, with surprises opening up as you do the puzzle. Many are very tricky (but fair), and some will have you berating yourself for missing something that should have been obvious, especially in the most challenging puzzles. For pure fun, without the frustration which trailing produces in many of us, this is one of the best books around.
My only problem with the book concerns the spiral binding. Very soon after I started working the Demanding and Very Challenging puzzles in the back of the book, the back cover and some of the answer pages started releasing themselves from the spiral. After many annoying episodes of this, I finally released the back cover and let it hang loose. (It didn't make any difference to the book's sturdiness.) I put the pages back into the spiral, and then used household wire to overcast the spiral completely closed. That held the pages in place and solved the problem. n Mary Whipple
