My student daughter was looking for a good place to sell her old University Books, and was fed up with the sky high fees that sites like Ebay charge, so I searched the web and found the ideal solution at

Bookex is basically a free online market place (or classifieds) that allows students to buy and sell University books quickly and easily. The best difference between Bookex and other auction or classifieds site is the fact they offer free listings, meaning that students can advertise and sell their books without cost.
Bookex does offer a Paid listing option for anyone wishing to create a bigger impact with their advert.
Bookex offer three different types of upgrades for the listings, a highlighted version which boosts the look of your advert with an orange highlight around it, a top-of-the-page listing which means your book will be listed above the competition, and a featured listed which means your advert appears on the homepage and tops your chosen category too.

To place an advert for one of your unwanted university books you’ll need to register for the site, then you are free to start uploading books for sale. You follow a simple step by step wizard to complete your advert and enter your book details such as ISBN. You also include the University you are at, the subject you are studying, details about the book a picture of the book and of course the price you want for the book.
The website has an internal messaging centre for buyers to contact you, and arrange to meet up and exchange your books for their cash, in a safe place of course.

It’s a great website, simple to use, and seems like the perfect place to buy & sell University books.