You may read the books for free online and even add your own annotations. Chasing prices can save you money, but if you drive all over town and spend many hours in the process, you may not save as much as you think. If you find them in fifty audio books or more do you think they may be good? When you start searching for textbooks on the site, you will notice that most of the listings are books for sale, but sometimes people will post books that they need to buy.