My friend eats, sleeps, goes to the bathroom, during school, he plays this card game.

http://www.elementsthegame.com/

Alright so after FINALLY getting to play Hearthstone ( I only just got it to work today ) I can say this game is the shizzle nits so far. It's very fast paced and easy to pick up on, it's a lot like WoW in that there's just the right amount of depth. It's not some overly-simplistic game for toddlers, yet it's got enough strategy involved to where you have to do some deeper thinking in certain situations. Just came out of a game where said thinking allowed me to make an epic comeback sitting at 5 health against an 18 health opponent within two turns, I feel pretty #MLG after that game.

If you're a card game fan I can honestly say I don't see any reason not to try this game once it releases ( if you can't get closed beta access ).