Juggernaut Amazon is striking another blow at the traditional textbook industry by offering semester-long rentals of physical books. The listings for a number of textbooks now include a “rent” option that’s usually around $50 for a title that sells for $170. According to Amazon’s FAQ, the books are rented out by the semester (counted as 130 days), with one 15-day extension allowed. Textbooks are shipped at standard prices, and the cost of returning them is paid by Amazon. Depending on their luck, renters might receive a book that’s new or one that’s gently used.