I assume you mean a "discount" for your room. All the Ent. books come with a card in the front of them. You need this card in order to get your discount for the room. You will have to show the card at check-in. You can book the room without the card, but they DO require / ask to see it when you check-in. There is no "coupon" needed, nor is there one in the books. Just as an fyi........... any books card will work.
Hope this helps!!!