Returning for a thirteenth volume thanks to continuing demand, Sudoku 16x16 Volume 13 contains 50 more attractively-designed large 16x16 Sudoku puzzles. Every puzzle can be solved just by observation - you don't need to make any pencilmark notes in the grid if you don't want to. At this size of puzzle that's really important Just place 1 to 9 and A to G into each of the rows, columns and 4x4 boxes. Visit www.sudokuxtra.com for more books in the series.