There is a slight card-based theme to this game, but it is not a card-based RPG.
Items, attacks and spells are represented by a card. When you find an item, instead of that item being buried in some menu, you'll turn it into a card. Really, its the same thing, except in card form you get some neat artwork.
While in battle, the only real card-based limit is the number of cards you can hold in your hand at once... this can be increased as the game progresses. The rest of the fundimentals are fairly traditional RPG mechanics... pick an item or attack and create a combo. Every card has a number in the corner (later cards will have multiple selectable numbers), when play the cards and create a pair or a straight you recieve a bonus. You only have so much time to create a combo and later in the game that time decreases. Also, the card will age and change over time. Food will rot, plants will grow, etc.
Now, let me toss out a quote from a Namco rep. "One of the advantages of this battle system is that strategy really opens up as opposed to getting slimmer. So in a menu-based RPG, you use a lot of strategy at the beginning because you're really weak. But near the end, you're so powerful you just use the same three attacks over and over again. With this, it's the opposite. We start you off simple and you can play two cards at once. Then you gain levels and you can lay down more cards, so by the end you're using the maximum amount of strategy, which keeps the gameplay fresh. It also makes the game more fun as you go through it, right up to the last boss." Phil Cohen, Nintendo Power, vol. 185, pg 47.