Book excerpt: What more perfect Christmas gift for sudoku fans than a book devoted to their favorite puzzle, ingeniously modified to celebrate the holidays? The clever elves at Conceptis, a world leader in puzzles and games, have overlapped regular sudoku grids to include holiday images like Christmas trees and snowmen. The overlapping creates a new kind of interaction between the sudoku puzzles, providing a solving experience unlike anything else out there. Grab some eggnog and get ready for some Christmas-crafted conundrums.