This is an excellent addition to the range of games available on the DS.
The single player is incredible, with a wide range of characters, vehicles and levels. Balloon Battle mode is also quite fun, and on hard mode takes some clever play to evade the barrage of red shells launched at your unfortunate character...poor Toad. He never had a chance.
The maps are diverse, and many have shortcuts which can be used to sneakily grab 1st position. My personal favorites are Bowser Castle and Peach Gardens. There is a total of 32 levels altogether.
The playable characters are all the usual Nintendo suspects - Bowser, Toad, Mario, Luigi, Peach etc. Some characters need to be unlocked, and there are nine characters in all. A wide range of different karts can also be unlocked.
The range of weapons is good, however the Blooper (which squirts ink all over your screen) can get annoying at times. Spiny (blue) shells are also exceptionally frustrating; however there is one way to avoid them. This is pretty hard to pull off, however, when you know there is a Spiny Shell headed your way, start powersliding, get your wheels on fire, and just as the shell is about to land on your head release the button and mini-turbo away from the blast radius. I've correctly executed this about 3 times (out of about 25 tries.) All the other standard weapons are there; green and red shells, bananas, bombs, lightning, mushrooms etc.
The only bad thing is that the game gets a bit easy once you have played it for long enough.
Overall, an excellent game.