Well, THIS is a game that retraces itself back to the beginning. One word best describes this game: INCREDIBLE!
Since the game is a prequel to the entire "Kingdom Hearts" series, I'd have to say this game was worth it. It would explain the early roots of the game's entire series -- WAY before the main character Sora could ever get his hands on a keyblade of his own. So, apparently there were three keyblade wielders that came before him and are out searching for a certain someone.
As the story progresses further, it would explain more on how things came to be in the later games. I have to say that the actual gameplay may seem complex at first, but the graphics were amazing, voice actors were well-chosen, and the storyline was incredibly written! Everything we came to know in the "Kingdom Hearts" series will all be traced back from the beginning.