When you play a card on someone, they should be allowed to read the card so that they can make a decision based on the outcomes presented. For those of you who think it would be more 'realistic' or 'RPG-like' to keep this information secret, just imagine a few games in when one player gets to know the cards. And you then play with a new player who doesnt know the cards - they are at a big disadvantage.
Like all other cards in the game, all players should be able to see them, read them, etc.
There is nothing in the rules that tells you to draw the card, keep it secret and only read out certain things from it. All games that I have that should be played like this specifically state that in the rulebook.