我不知道你有没学到微观里的elasticity的概念.
其中有一个perfect inelastic demand ,this means that demand for the product is not affected by changes in prices. according to your question where it sates every student will at most buy one textbook therefore, demand curve will be illustrated as a vertical straight line, even price of book drops, it is not affected on quantity demanded for book.example includes monopoly
while, it is certainly contridicted to the law of demand which states an inverse relationship between the price of a good and the quantity demanded of that good.