Ascension is one of the best asynch games on the platform IMHO. It is not really like Magic. It isn't a "collectible card game", rather it is a "deck building" game like Dominion (though it plays pretty differently from Dominion - it's a lighter game than that).
One key difference being that you don't buy (with real money) your way to victory. Rather everyone has access to the same pool of cards and everyone starts with the same cards in their deck. As the game progresses you "buy" (with "runes") cards to add to your deck, and try to build a deck that will win the game for you. Thus "deck building". It does look like Magic as it was designed by some Magic players, but it is a different type of game. I don't enjoy games like Magic much, but I love Ascension.