Kakuro to Go by Nikoli Publishing, Puzzler Media, Nikoli Publishing
Kakuro are crossword puzzles with numbers, with all the clues in the grids. As in Sodoku, logic plays a big role, and there is only one correct solution. But the process of solving them is much like that for a crossword: All the squares are blank in the beginning, and you fill in the numbers as you would letters in a crossword, based on meeting the totals given for each row and column.
So take KAKURO to Gowith you a few hours of high-quality entertainment on your commute, over lunch, or wherever the puzzle craze hits.