It's a realtime strategy RPG, combining elements of the classic FF battle system with a stylus-driven method of assigning individual orders to a fairly substantial party of adventurers. Despite the odd problem, this is an exceptional DS game. The story'll make more sense if you know FFXII, as there are loads of recurring characters and references to past events, but it's not essential.
You don't even need to be mad on FF or strategy games in general, as this is very much its own thing. Simple, accessible, funny and good value for the playing time it offers.