I've said it before, I'll suggest it again:
Well advertised in advance, it's a perfect fund-raiser for some organization. My frat (Alpha Phi Omega) did this and made THOUSANDS of dollars each semester.
We had a 4 day book sale at the beginning of each semester, including the Sat and Sunday before classes started. The first day was "bring in your books" day. We put a sticker on the corner of each book with the seller's name and the price that *THE SELLER* wanted for the book. We sold them on commission: if your book sold (at your price), we got $1 for the sale. Sales were the last 3 days, although, students could still bring in books to sell during those days.
Some books, of course, didn't sell. These would typically be the ones that were no longer used (and of course, the book stores wouldn't have bought them back anyway.)
However, from the student standpoint: Bought new from book store for $100. Sold at our sale for $60 (bookstore would have only given 40). New buyer bought for 60. Resells following semester for $60. Next new buyer resells for $60.
Compared to the used book price of $80.
So, each student paid $20 less than the book store's price. And, each student sold for $20 more than the book store would have paid. Win-Win situation for the students.
The only one who loses is the bookstore which was making $40 per book by holding on to them for 2 or 3 weeks between semesters.
Being a member of the organization that ran the sale also had benefits: you could pick the cheapest book in the pile (each person sets their own price) and the following semester, you could figure out the maximum price you could ask for your book and still sell it. Thus, I made a *profit* on my textbooks each semester. i.e. bought books for $200, sold previous semester's for $250. Lather, rinse, repeat, profit. Plus, the bookstore won't buy back books with torn off covers, etc. You know as well as I do that if the bookstore is selling it for $80 used, but you can buy it without a cover for $25, you're going to jump all over the coverless version, unless, perhaps, it's a book you want to keep.