Fullmetal Alchemist: Trading Card Game on the DS suffers from its source material on two different levels. First, the original property, Fullmetal Alchemist, doesn't really lend itself to a card game. Fullmetal Alchemist, for the uninitiated, is a show about two brothers who attempt to use alchemy to revive their dead mother, but fail and accidentally maim one brother and trap the other brother's soul in a suit of armor. Then they have adventures!
The card game, then, revolves not around simple competition with adversaries, as would be expected of card games; or rather, it does, but altercations are treated in the card game's "storyline" as ancillary to the goal of locating the powerful alchemical relic, the Philosopher's Stone, and fixing their bodies. Perhaps, then, FMA was not the ideal choice of properties to translate into cards.
Second, the DS game suffers by being such a faithful translation of said card game, which, to be blunt, is far too complicated to be worth attempting. The DS game makes valiant attempts to streamline the process and teach the game, but every person on Earth who has a strong enough interest in Fullmetal Alchemist to learn the card game has done so, and nobody else has any reason to try.
Each round of gameplay consists of six phases (seriously.) A few of those phases are divided even further. The phases dictate when you draw cards, recruit allies, level up your characters (again, seriously) and initiate battles. Your success in any of these phases is determined by aggregating numerical stats found on each of the cards in ... some way. A big jumble of mysterious icons tracks these numbers on the side of the screen, but it's pretty hard to remember which stat Red Circle With Fangs tracks versus Stopwatch Thing. This becomes less of a problem as you get used to the game, of course.
For their part, developer Magellan Interactive did a good job of putting the card game into the DS. If you can somehow manage to get over the initial hurdle of not understanding what the hell is happening, the game offers nice features that assist with the card game. You can select from a number of pre-made decks, each associated with an FMA character, or you can build your own decks and save them. You earn more cards through victories in story mode. In addition, there is a "Fantasy Mode" in which all 500 cards are unlocked. Perhaps most importantly, the game features online play.
If you're an avid player of the Fullmetal Alchemist card game in real life, this is an easy decision. Buy this game. It has all the cards available after only one purchase, so you're free from the tyranny of boosters. Also it's got online play, so you may finally be able to find some other crazies out in the world to play it with. Not to mention it automates gameplay and keeps track of what phase it is and how much Leadership you have and all that stuff.
It's difficult to recommend this game to anyone else. It is possible to play the game, eventually, but you need strong motivation to learn, which, for most of us, is not contained within the gameplay itself. You may as well go the easier route and actually learn to transmute metals into gold.
Final verdict: 5/10
(Final verdict for existing FMA card game players: like a million/10)