Although it doesn't follow the story of the TV series perfectly, it still offers a very fun and adventurous game.
First, the story. You start out as Gohan, but later on throughout the story you will be able to switch between characters to access areas that were previously locked. You will eventually be able to play as Piccolo, Goku, Vegeta, Trunks, and the world champion, Gohan's future father-in-law. The game starts out directly after the events on planet Nanek after Goku defeats Freeza and all the way up to the defeat of Cell. It doesn't follow the story perfectly, but that's not always a bad thing. One of the flaws of Buu's Fury was that it tried to copy the show exactly, and it really didn't come off that well. However, in this game, there is a lot of extra content that fills you in on the past of Goku. All in all, even though it doesn't follow the show exactly, what it offers is very good.
Second, the gameplay is just right. It is very easy to pick up and play. Every character that you play as has their own select moves that you unlock as the game goes on. For example, Piccolo has his signature "Special Beam Cannon" move, while Goku and Gohan both have the well-known "Kamehameha" blast. All the moves work differently and are fun to use and see. Switching through these moves is easy: all you have to do is press the L button to switch between special moves. Also, later in the game, you'll be able to have your character go "Super Sayin" for a short period of time. Both going Super Sayin and using your special moves costs energy, but you get more energy the more you level up.
Another feature is that you can equip your characters with items that can effect you. This add another level of depth to the gameplay. They can add energy, or affect a certain move. Some items will only work when equipped to certain characters. It isn't hard or technical at all.
Over all, the gameplay is very solid, and works perfectly.
The graphics are good. You can recognize all your favorite DBZ characters immediately. They aren't the best on the GBA, but they are still good at what they try to show and do.
Overall, if you are a DBZ fan, you should get this. This is a surprisingly strong Action-RPG that you can easily spend over 30 hours on if you try to complete everything. It is really one of the best games on the GBA.