An amazing game... and I haven't even played Multiplayer yet!
The gameplay is very similar to all other Mario Kart games. The one major difference is the aspect of drifting, and gaining boosts by doing so long enough. This adds a great level of difficulty to totally master the game, while the game is very easy to pick up and play right out of the box without reading the manual or going through a tutorial (which there isn't one anyways =P).
MK: DS is filled with many unlockables, including carts, racers, and some of the Grand Prix modes must be unlocked as well, by winning the previous ones. I have unlocked all but one Grand Prix, but have only unlocked 1 racer, and that's after playing for about 15 hours. However, I haven't been trying to unlock items - I've been taking my time and enjoying ALL the options MK: DS has, which there are many of.
There are battle modes, VS modes, time trial, grand prix, and last but not least, WiFi multiplayer. While I have not played on WiFi yet, I heard it adds to the gameplay even more. However, I feel this game is perfect even without the online play, which I will try as soon as I get the WiFi USB cable.
This game is very easy to pick up and play for either a few minutes or many hours. With the wide varieties of game modes, you wont get bored with this game for a long time. The value of this game is amazing, and it is a DEFINATE must own for any DS owner.