Puzzle in words: there's a grid of dots, some of them with a number, between a square of four. The idea is to draw one linking line so that every number is surrounded by that many filled-in sides. There's only one possible solution to each puzzle, and every one can be fiendishly difficult to discover. What's more is that Puzzle Series Vol. 5 comes loaded with hundreds of them.
What makes them so great is the pure logic that's required to solve them. There's no guess work, as recently made popular by various Channel 5 not-actually-a-quiz gameshows, and you'll never feel more clever than when finishing a tough one. The Japanese menus are easily navigated, and it's all crystal clear. They'll make your mum's Sudoku puzzles hide in shame.