Draw cards equal to the number of cards in your library, then put a card from your hand on top of your library. You have no maximum hand size until your next turn.
1/24/2013 You won't have to discard any card during the cleanup step of the turn you cast Enter the Infinite. You will have to discard down to your maximum hand size during the cleanup step of your next turn.
1/24/2013 If you are playing with the top card of your library revealed (due to Garruk's Horde, for example), you'll reveal each card before you draw it.