Most Universities along with campus bookstore shut down at the beginning of the Covid-19 pandemic. Some stores are offering contactless pickup for online orders, but other services are not available. That means you can't just brings your used books in and sell them back at the end of the semester like normal. This presents a logistical and financial challenge to college students.
Sell Them Online
Over twenty online companies are ready to purchase your used textbooks, and they will send you a free shipping label. One of these companies - ValoreBooks is the same company that operates the textbook department at most colleges and universities in the U.S. All these twenty plus companies compete in a bidding war online for your used books, and you can
compare all their offers here. Just enter an ISBN and you can search offers from all these companies in one place.
Get More Than You Would at the Bookstore
When selling textbooks, it's best to shop around for the highest offer because the discrepancies among buyback companies can be huge. At the University of Georgia, the campus bookstore offered me a very low price for a book for which I paid over one hundred dollars. So I walked down the street to an off campus bookstore, and they gave me around seventy dollars more than what the UGA bookstore quoted me. It works the same way online, and it's all about inventory. If one campany has an oversupply of a particular book, they will pay less for it. Another company might have a shortage of that same book, so they will pay more.
Sell to Multiple Buyback Companies
Maybe you have four or five books to sell at the end of a semester - don't think you have to sell all of them to the same company. Send one to ValoreBooks, one to BookByte, one to eCampus etc. Compare prices and do what you can to get the most money back. However, some buyback companies have a minimum order value - to get free shipping you must sell them a minimum value of textbooks, say fifty dollars. This can very among vendors and some don't have a minimum so check their 'Add to Cart' and see if you see anything about an order minimum. This prevents them from losing money by purchasing, say a twenty dollar book, and paying ten dollars shipping.
Trade with Other Students
Maybe this isn't possible, but another option is to trade textbooks with your friends that need the same book next semester. If you are in your third or fourth year and taking classes for your major, chances are you know many of the students in your classes. Everyone takes different classes different semesters, so chances are someone you know needs your textbooks and you might come out better than selling them back to the book store or online.