Hexadoku: Sudoku with a hexadecimal twist

Hexadoku is a challenging variant of sudoku that uses the set of sixteen hexadecimal digits, instead of the traditional nine. It is played on a 16x16 grid, which means there are over three times the number of cells that need to be filled in! No knowledge of hexadecimal is needed to play... just a bit of logic and a sharp pencil. (This book contains three hundred hexadoku puzzles grouped into four difficulty levels.)