To me, this the weakest game in the series.
The game immediately takes place after the events of the first game when our heroes Sora, Donald, and Goofy go searching for Mickey Mouse and Rikku. Along the way they come across a mysterious castle known as Castle Oblivion. Upon entering the castle they begin to lose their memories and they must venture through familiar Disney-themed worlds and stop whoever is behind this. So far so good. But then came a tutorial for the new card battle system. I do understand that it was trying something new, but I just didn't like it as much as I thought I would. The experience I had was rather hit-and-miss, so I would consider this to be the weakest game in the series.
PROS:
-Wonderful graphics for GBA
-Good sound and music for the most part
-Controls well
-Story sticks
-Once you get used to the new card-battle system, the action is pretty good.
CONS:
-Almost everything is recycled from the first game
-I wasn't fond of the card battle system
Problems aside, this game is still recommended for fans of the Kingdom Hearts games. Those who want a good GBA game for their library should rent it first and decide for themselves. You'll most likely come across a few annoyances in the game, but they shouldn't ruin your experience.