Obtaining a discount card in return for paying a certain amount
Question

                In some bookshops there are advertisements for a scheme whereby the customer pays a set amount of money each month and gets two things: he will be supplied with new books in a specific area of interest, such as fiqh, etc, and he will get a 10% discount if he wants to buy books from these stores. What is the ruling on this?
Praise be to Allah.This is a kind of gambling, concerning which Allaah says 
          (interpretation of the meaning): 
“O you who believe! Intoxicants (all kinds of alcoholic 
          drinks), gambling, al-ansaab (stone altars for making sacrifices to 
          idols, etc.) and al-azlaam (arrows for seeking luck or decision) are 
          an abomination of Shaytaan’s handiwork. So avoid (strictly all) that 
          (abomination)…” [al-Maa’idah 5:90]
Gambling means everything that involves one side trying 
          to take advantage of the other, so that one will be the winner and the 
          other will be the loser. This is the shar’i ruling on gambling. So a 
          man who pays 500 riyals every month, for example, may buy books for 
          which his discount adds up to more than a thousand riyals, or he may 
          not buy anything at all. If we suppose that he buys things for which 
          the discount adds up to more than five hundred riyals, then he will 
          be the winner, and the storekeeper will be the loser; if he does not 
          buy anything, then the storekeeper will be the winner and the man will 
          be the loser, because he paid 500 riyals and did not get anything in 
          return. This transaction is a kind of gambling and is not permissible.