Christopher Tobin’s TO81 PUZZLE BOOK provides a set of 31 puzzles, grading from easy puzzles at the beginning to more difficult ones near the end. They combine both crossword and Sudoku strategies, culminating in a final set of four anagram puzzles. The reader would be well advised to do these puzzles in pencil, not so much for the crossword clues but for the Sudoku portion. It’s a lot easier to write in multiple possibilities and then erase the numbers that don’t work in the end.

Instructions are clear, easy to understand, and detailed.  Which is useful because these puzzles are not quite like other puzzles the reader may be accustomed to, and it’s a good idea to be fully aware of all the differences beforehand. Unlike standard crossword puzzle clues, these give both a direction (sometimes diagonal) and a word length. A line of spaces to be filled in one given direction may include multiple or even overlapping words, keeping the solver on their toes. What one enters into the puzzle, though, are not words but numbers corresponding to each letter of a word. These will then be used in the second part of each puzzle to find the missing numbers for the remaining squares, Sudoku-fashion, with each number appearing once and only once in each row and column.

Translating the letters into numbers feels awkward at first, but it's not too difficult to get accustomed to—especially since Tobin has deliberately chosen letter-number correspondences that look relatively similar (0 for O, 1 for I or L, 2 for Z, etc.). There’s also a reference guide on the side of each puzzle. The main difficulty arises when using already-entered numbers to guess at other crossword clues, as the puzzler has to retranslate the numbers back into letters, and the visual clue of a partially completed word is less obvious. Crossword clues, even in the more challenging puzzles, are not too difficult to guess at; some of them are downright obvious, especially the acronym ones. You don’t have to think too hard to realize that the acronym for, say, American Business Corporation is ABC (not an actual clue).

The Sudoku-like portion is where the real challenge arises. Especially since, unlike in actual Sudoku, there are no 3×3 boxes to use to eliminate possibilities: only rows and columns. Another slightly confusing issue is that the 12 available numbers go from 0-9 and 11-12, skipping 10—which can add a little mental hiccup to the elimination process. The anagram puzzles at the end provide a satisfying conclusion to the whole book, tying together all the puzzles and leaving the solver with a feeling of completion and accomplishment. All in all, this is an entertaining and novel way to combine puzzles that will provide the adept reader with a reasonable degree of challenge, as well as an engaging excuse to use multiple types of problem-solving skills together.

The puzzles in Christopher Tobin’s TO81 PUZZLE BOOK are a delightfully complicated mix of crossword and Sudoku, challenging enough to stimulate the brain without being frustratingly punishing.

~ Catherine Langrehr for IndieReader