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.