Non-Consecutive Sudoku - Puzzles With One Extra Rule That Transforms Everything Non-Consecutive Sudoku looks like regular Sudoku. But there is one powerful extra rule: no two consecutive numbers may be placed next to each other — horizontally or vertically. So 5 cannot sit next to 4 or 6; 1 cannot sit next to 2. This single constraint transforms the puzzle profoundly, opening up new deduction pathways and eliminating techniques that work in classic Sudoku. Volume 2 builds on the first book with all-new puzzles and more variant types: Classic Non-Consecutive Sudoku - Non-Consecutive Jigsaw, Diagonal, Killer - Double Ring and Butterfly variants - Flower Sudoku variants Format & Paper 7 x 10 inch pages, thick paper, instructions, all solutions. One Extra Rule. Transforms Everything. Volume 2. By DJAPE — PhD in Computer Science, Washington Post puzzle contributor since 2006. A delightfully tricky gift for Sudoku solvers who want something subtly and surprisingly different!