A gentle course for beginners and for casual solvers who get stuck halfway. Eight short lessons, one solving technique at a time, each followed by 15 puzzles that need that technique to finish. 120 puzzles in all, one per large page, with full solutions at the back. Paperback, 8.5 x 11 in, 142 pages.
The grid has 9 rows, 9 columns and 9 boxes of 3x3. Fill every empty cell with a digit from 1 to 9 so that each row, each column and each box contains every digit exactly once. That is the whole rule. No math is involved; the digits could just as well be letters.
Every puzzle in the book has exactly one solution and can be solved by logic alone. You never need to guess.
Pick an empty cell and look along its row, its column and its 3x3 box. Cross off every digit you can see. If eight different digits are visible, the ninth is the answer. Each digit you place removes that digit from the cells around it, so new naked singles appear. Fill one cell, then look at its neighbors again.
A good place to start below: the first cell of the second row. Its row, column and box already show eight different digits, so only one is left. There are five more cells like it on the board right now.
| 4 | 5 | 2 | 8 | |||||
| 3 | 8 | 9 | 5 | 2 | ||||
| 6 | 7 | 2 | 3 | 8 | 1 | 9 | ||
| 3 | 6 | 4 | 2 | 7 | ||||
| 7 | 2 | 1 | 8 | 5 | ||||
| 9 | 4 | 8 | 2 | 3 | 1 | |||
| 6 | 7 | |||||||
| 4 | 9 | 5 | ||||||
| 7 | 5 | 9 | 3 | 2 |
| 4 | 9 | 5 | 2 | 1 | 7 | 6 | 8 | 3 |
| 1 | 3 | 8 | 9 | 6 | 5 | 2 | 7 | 4 |
| 6 | 7 | 2 | 4 | 3 | 8 | 1 | 5 | 9 |
| 3 | 8 | 6 | 5 | 9 | 1 | 4 | 2 | 7 |
| 7 | 2 | 1 | 3 | 4 | 6 | 8 | 9 | 5 |
| 9 | 5 | 4 | 8 | 7 | 2 | 3 | 6 | 1 |
| 5 | 6 | 3 | 1 | 2 | 9 | 7 | 4 | 8 |
| 2 | 4 | 9 | 7 | 8 | 3 | 5 | 1 | 6 |
| 8 | 1 | 7 | 6 | 5 | 4 | 9 | 3 | 2 |
After naked singles come hidden singles, naked pairs, pointing pairs, box-line reduction, hidden pairs, naked triples and the X-wing. Each lesson has a worked example from a real puzzle, and the puzzles inside a lesson run from gentler to tougher.