Final Fantasy XIII Novel: Episode Zero: Promise (novel)

Before destiny was decided...
In the futuristic society of Cocoon, all the needs of the people are taken care of by the godlike fal'Cie. The only threat to their comfortable lives is the world of Pulse below, ruled by its own fal'Cie with their own intentions. And should trouble ever arise, the fal'Cie sometimes choose humans to do their bidding-and life will never be the same for these people marked by fate.
Before the unlikely heroes of FINAL FANTASY XIII banded together, each had their own story to tell. This series of short stories chronicles the last few days before their encounter with a fal'Cie, providing a deeper look at the characters of the hit game!