The value of giving up the next best option is known as the opportunity cost of a certain activity. The value of the best possible alternative activity that could have been completed during that time, such as taking a nap, is the opportunity cost of reading Chapter 1 in this instance. Your opportunity cost per chapter does not necessarily go up if you choose to read an additional chapter today. The value of the next best option lost is still the opportunity cost. Nevertheless, since you are forfeiting more time that could have been used for other pursuits, the overall opportunity cost does go up