Purists will hate it, but if you give it a chance you'll find it has deep, engrossing gameplay underneath the namesake.
Avoiding any long discussions on the various cards, since there are over 500 of them, the environments are set up like a chess board. While they are in 3D, they are set up in squares. Snake must move either left, right, up, or down, but he still has the trademark crawl and wall press. Snake must also turn his facing rather than just moving and ending up in the facing you want. It can be a bit annoying at times, but you get used to it. The most important factor of the game is that it is turn-based. Since all the rules apply to you, they apply to enemy as well. Enemies, while for the most part never having to worry about weapons, still can be disarmed and follow all the same environmental rules as you. I've personally seen guards slip on oil patches and get themselves covered in it, so you can feel safe in using the environment to your advantage. There's the trademark alert, evasion, and caution modes you've come to know in the series, but since the game is turn-based, often one can quickly get away from the guard or whatever issuing the alert and quickly find a place to hide and recover cards in the meantime.
The game has an interesting graphical look, but it's nothing to get excited over. Often the camera controls are limited and can cause quite a bit of confusion. Character models look excellent up close, but tend to look grainy and pixelated from a far. The colors are vibrant, almost too vibrant for the traditional washed-out look the series has. Environments look pretty bland as well. For better or worse, the graphics are simply there. They don't really stand out, nor are they terrible.
Sound is lacking in the game as well. You'll find the standard music from the game such as when in alert mode, but there is no vocal work for the game. You're going to be reading a lot of text and that can be a major turn-off to quite a few players that have become accustomed to long-winded vocal acting of the series. Still, the sound effects are decent and more or less the sound is in the same league as the graphics.
There's actually a quite a bit of value in the game. There are incredible amounts of cards to collect, especially the secret ones like Metal Gear Solid 4 cards. There is the Solid Eye mode which uses a cardboard 3D viewer that comes with the game to play certain aspects of the game and videos on the disc in 3D. The game includes a trailer of the upcoming fourth game and link to view pictures taken in the Subsistence version of the third game in Solid Eye mode. There's no manual in the American version on how to do this so you'll have to search online to find out how. Without going into details, it's actually quite easy.
The story for the game pretty much parallels the first Solid game in many ways and you'll probably not be as enthralled as with the canon material. The game has a steep learning curve, but I suggest you don't let that discourage you. It retails now for $20, but I'm willing to bet you can find some used or in bargain bins for less, so either way it's worth picking up.
The good: Deep, turn-based, card gameplay, incredible amount of cards to choose from, forgettable but enjoyable story, decent graphics.
The bad: No vocal work, frustrating camera, may be overly difficult for new players.