Advantages: Make money fast, without much effort. Get more money than if you were to resell them to a used bookstore or to a college bookstore if they are college books.
Disadvantages: Having to take the product to the post office to ship out. People questioning the legitimacy or authenticity of the product you are selling. With all the scams on things such as: Makeup and perfumes, it is getting harder to trust what people are selling.