For anyone who is or has been in college, books are a heavy (literally and figuratively) necessary expense. One of the worst parts is that most books that are required for courses are not books that you would want to keep in your library after you finish the course (do you want to lug around or ever reread a book on accounting or biology?)
In the olden times (when I went to college) we used to resell our books to the bookstore as a way of recycling our textbooks, but we would get only a few cents on every dollar we had spent on buying them. Sometimes we were lucky enough to find a used textbook, but it was usually marked with highlighter and notes in the margins that were more annoying than helpful.
There is now a company that rent books! Bookrenter has filled a niche market by renting books to students for various lengths of time (week, semester, year) for a fraction of the cost of buying a new book. Students can save about 75% off the price of a book by renting a book they probably don't want to own anyway, and they get a pristine (no highlighter, no notes in the margins) copy. No need to try to sell your book after your course, you simply return it to bookrenter just like a DVD. The concept is just like Netflix, but for anyone enrolled school with an average annual book bill reaching $1000 per semester, this is much more practical, and with the savings you can actually afford to rent a movie!
Books that are worth rereading are worth buying, but for any other book, renting is better than buying.