You'll have a fun time.
It has good selection of characters from the mario franchise.
In this game there is know loosely put together story as you see in other games its pure racing madness. In the race you hit blocks as you run through the various tracks to get items to help you during the race. These items are for the most part are randomly selected if u tap the item button quickly it will speed up the roulette of items to choose one faster. If you are in firstt place your items get decreasingly worse mainly due to you being in first. so if your in first don't except thunder bolts and red shells.
There are 3 default cups in MK:DD Mushroom,Flower,and Star. You can unlock 3 more bonus cups Crown,All Cup, and Mirror.
Along with the cups u have a speed selection which i've almost never seen in another racing game. you have 50cc 100cc 150cc along with the increase of speed so does the difficulty in the AI the once seemingly sucky and horrible Bowser will soon shock you when he takes over you in this setting.
As you beat cups on all the difficulties you unlock more cars,characters,levels,etc...
The Single or Co-op Cups will be short lived if you try and have enough time you can beat the game in a day... the game is EXTREMELY SHORT.
But where the Cups fail the Multi-Player Picks up if you can get 4 players locally or if you are lucky enought to have a gamecube link cable tou can get 8.
The Multi-Player racing works the same way the single does excpet with your friends and the fast changing place postions and crazy items will have you screaming and jumping up and down with excitement.
But in Multi-Player its not all racing there is a battle mode where you different options. you are still in karts and have the same characters but they mixed it up a little they have u fightin each other by throwin bombs at. or who can survie with the most ballons. and other crazy game types.
All in all if you don't have play this game in multi-player with your friends you really aren't getting the most out of Mario Kart.