I played around a bit with one starter box of the World of Warcraft Trading Card Game, duelling against a friend. Each starter box comes with a simple 30-card deck, two packs of boosters, and three oversized hero cards, which can be used like the normal ones. WoWTCG plays a bit like Magic the Gathering, in that you have a deck, a hand of cards, one opponent, and the goal of the game is to deplete your opponents life points. Compared to Magic the Gathering it is a lot simpler.
Your hero is the most important card, and isn't shuffled into your deck, you start with him in play. Your hero determines whether you are Horde or Alliance, and he also has a character class. Your faction and character class determine what other cards you can put in your deck. I got a night elf druid, so I can use Alliance allies, spells like Mark of the Wild, and leather armor. Most of the cards in the boosters were spells or abilities for other classes, or items a druid can't use, so I would need to buy a lot more cards before I have a deck for every character class. Good business for Upper Deck Entertainment, but expensive for the players.
You start a game with 7 cards in hand, and you draw a card every turn. To play cards, you need to pay their power cost, and for that you need resources. The best resources are quest cards, because you can later play them face up and later do whatever the quest demands to get a reward, like drawing another card or shuffling your graveyard into your library. But if you don't have quests, you can play *any* other card face down and use it as resource. As you are unlikely to not have any cards in hand at the start of the game, you can count on having one resource in play on turn 1, two on turn 2, three on turn 3, until you don't want to play resources any more.
Cards you can play are allies (creatures), items including weapon and armor, or abilities. After doing that, you usually want to start a combat. Unlike Magic the Gathering you don't just attack the other side in general, you get to choose a specific target. So you can decide whether you want to kill your opponents allies off, or go right for the opposing hero. Only if your opponent has allies with the "protector" attribute can he intervene in your choice of target. Some allies are "elusive" and can't be attacked. Every ally has an attack value and a number of health points. Any damage you do is permanent, marked with counters, so a tough defender can be killed in several rounds. And of course there are healing abilities to remove counters. Battle rages back and forward until one hero runs out of health and his opponent wins. Relatively simple and straightforward. An online demo on how to play can be found here.
All the classes, abilities, items, and quests are taken from the World of Warcraft MMORPG, and that is the main interest of the WoWTCG. If you don't play WoW, stay well away from the trading card game, there wouldn't be much interest, there are much better trading card games around. But for WoW players the idea to play "offline" might be interesting. And to lure these WoW players to buy more cards, Upper Deck Entertainment is also adding a UDE point or loot card to every booster, giving you WoW in-game items, which are purely decorative. Although your best bet to get these might be EBay.
Having played Magic the Gathering for years, I wasn't impressed by the World of Warcraft Trading Card Game, it is too simple for my tastes. Buying more cards gets expensive without getting more intricate. But if you want to have a look, buy two starter boxes and play an afternoon with a friend who is playing WoW as well, that is fun enough.