Each player begins the game with a predetermined deck of money and a few victory points. Each turn, one draws five cards from the top of his or her deck, plays any action cards, then purchases new cards, and then discards all played cards (including any newly purchased) into his or her discard pile. As soon as the deck is depleted, one shuffles all the cards in the discard pile to form a new deck. Thus, as the game progresses, you are constantly adding cards to your deck, increasing your buying power and giving you new ways to interact with your opponent. Eventually, the game ends either when all of the most expensive victory point cards have been purchased or when two complete sets of action cards have been purchased.
In many ways, this feels almost like a Magic the Gathering draft in which you constantly alternate between drafting new cards and playing several turns with your newly drafted cards. In any one game there are only 10 distinct action cards to be purchased, along with three denominations of money and three denominations of victory points, so obviously the variety is much smaller than in a Magic draft. However, while not particularly complex, certain sets of cards create synergy with each other, allowing you to more quickly draw through your deck or purchase cards more quickly. In the base game there are 20 different action cards available, but only 10 are selected for any given game. And when these become too familiar, there are 12 more expansions that are available for purchase.
Another factor that makes this deckbuilding mechanic so interesting is that none of the victory point cards have any function in the game until the game ends. So if you purchase too many too earlier, they tend to clog up your deck, slowing down your ability to purchase and play cards.
The production values for this game are quite good. The artwork is vivid and strongly ties the game to the feel of managing a fantasy empire. The rulebook is easy to understand, comprehensive, and even suggest which cards to include for your first game. The box itself comes with interior plastic tray to keep all the cards organized while they're not in use. The cards themselves are solid cardstock, and feel remarkably similar to a Magic card. However, given the massive amount of shuffling that takes place in the game, one would be well advised to purchase sleeves to keep the cards in good shape.
Dominion is a great game, and one that I think will particularly appeal to those who enjoy Magic the Gathering. If you're interested, you can actually try the base game out for free at Goku.com. Give it a try - you won't be disappointed!