It's a massive shame that this game has been overlooked by the public in favour of less obscure titles. In short, The World Ends With You is one of the finest games I've ever played.
My own declaration actually puzzled me at first, because, it's strange, when you see what the game actually presents, gameplay wise, it's extremely repetitive. It's a lot of the same thing over and over again, with mild variations now and again, but the game somehow disguises this so well that you only notice when you really look. To pull that off in the first place is one thing, but the fact that the thing disguising the fairly linear gameplay is an absolutely fantastic story makes it all worth while.
The World Ends With You has an amazing story to it, coupled with a good sense of humour, interesting characters and plot twists. It is honestly worth getting the game simply to find out the story.
My previous mention of the gameplay is obviously negative, but regardless of being repetitive in the long run, it is indeed great. The gameplay consists of mainly two sections, walking in the overworld with mind-reading elements, and the battles. In which you can use special pins to give yourself (essentially) superpowers. It's a lot of fun, and if you take your time with it, the illusion of not being repetitive is all the more stronger.
Equiped pins can be levelled up typical RPG style, and get stronger and more effective, this all takes place on the bottom screen with the touch screen. It's entirely touch controlled, with different pins requiring different methods of touch. For example, with an ice pillar pin, drag the stylus upward on the screen to make a pillar of ice shoot from the ground. It can be slightly unresponsive, but examples of this were rare during my playthrough. On the top screen, is a second battle with a partner, controlled by the D-pad and buttons. You basically have to simultaneously battle on both screens. It can get overwhelming at first, but you'll get used to it. If you find it too hard, you can set it so they fight automatically.
The game contains other typical RPG elements, such as clothing and accessories that effect your stats. The food mechanic is a particularly interesting one. You can make your character eat stat-building food that digests as the battles go on.
Overall, this game is amazing and essential for any DS owner looking for something a bit different. The story will blow you away all on it's own, and there's plenty of extras and side-games to keep you coming back, not to mention the soundtrack is just awesome. A must-buy.