Is purchasing school textbooks, with the library offering the opportunity to resell them at a lower price after the end of the semester, or renting them for a fixed non-refundable amount, considered usury (riba)?

The first scenario (the student buying a book and selling it to the library after use): This sale is valid and free of usury, as long as the student purchased the book for cash for his need, or completed the payment of its price before selling it to the library, and did not buy it in installments to sell it for cash. The difference between the two prices is due to the decrease in the book's value from use, and not to the disparity in sale between deferred and cash payments as in a bay' al-inah (a type of re-purchase sale). It was reported from Shaykh Ibn Uthaymin - may Allah have mercy on him - in "Al-Sharh Al-Mumti" that it is permissible for a seller to buy back his merchandise for less than he sold it for, after receiving the price, or after its condition has changed, provided that the decrease in price corresponds to the decrease in condition, and is not due to deferment and cash payment.

The second scenario (renting books): Renting books is a permissible transaction, with no harm in it. It is a rental fee in exchange for the benefit of reading and perusal. It was reported from Ibn Qudamah in "Al-Mughni" and Al-Buhuti in "Kashshaf Al-Qina" that it is permissible to rent books for reading and looking into them, because their benefit is permissible and intended, and is utilized while the book remains. The Qur'an is an exception, out of reverence for it.