This game is great. It's my favorite Atlus game, and even though I can't give it a perfect rating, it is still one of my favorite games on the Playstation.
Kartia works similarly to Final Fantasy Tactics, because it is a strategy RPG (or SRPG) and focuses on a character type being stronger than another. Other than that, it's fair game. You can compare it to Tactics Ogre as well as any other tactical battle system.
One of Kartia's best attributes is its imaginative story. In the world of Kartia, magic cards (called Kartia) can be used to create anything from coffee to demons. You could compare this to how you use runes for magic in RuneScape. These cards act as disposable items you can collect over the course of each battle. You can spend them to perform magical acts from creating new characters and armor to summoning weather effects to attack an area of the battlefield.
Kartia features a fairly complex battle system, but it's easy to understand. You have the real characters and the golems. Each real character can level up and get very powerful, but if they die, it's game over. Golems are simply summoned allies and can be replaced, using the Kartia. This makes battles a little like chess: you try to use your pawns first and get rid of the opponent's pawns in the process.
In the end, the game draws down to the cards. Each card has its own symbol or glyph on it. These glyphs mean an element and have to be combined in specific ways to form magic effects. Again, it works like RuneScape's runes system. You get fire glyphs, water glyphs, wood glyphs and even rock or earth glyphs. You can combine these elements into armor, weapons, golems, and magical attacks.
The game even has multiplayer modes. Sorry, it's actually only 2-player, but it has that multiplayer feel. You can set up maps and play 1-on-1 or 2-on-2. When playing 2-on-2, you and your friend play on the same team but each control your own squad of characters. One small annoyance with these modes is you have to wait on each other, and it does get a little boring playing 1-on-1. However, you can import the story mode characters from your memory cards, offering a fun way to show off your character stats.
My only complaint is you do nothing but battle. Sure, you have lengthy story scenes, but you don't have any exploration aside from the turns you waste during battles to reach chests. This brings up a cool feature, though. You can use an ice spell to freeze water and then use a fire spell to melt the ice. This results in a new layer of strategy useful for both escaping the reach of enemies and reaching previously unreachable areas. Unfortunately, it doesn't offer much of a shortcut, you can usually walk around the water faster than you can cast your spells.
The music is great, very catchy. The sound effects are the best I've heard from any game on the Playstation. The visual representation of each character is superb, but some people might not like the isometric graphical style.
Overall, Kartia is a must-try game. It's hard to look at this game and honestly say anything's wrong with it. I can say that it's rough around the edges and could be improved a lot, but it's still one of the best SRPGs I've ever played.