In his book Debt-Free U, author (and former TIME Moneyland contributor) Zac Bissonnette says, “The average student spends somewhere in the vicinity of $400 dollars per semester on textbooks… Textbooks are updated regularly, often for little or no reason.” Bissonnette says he was able to save more than 99% on the cost of one textbook by buying it used. This advice holds true for other books, as well. Even runaway bestsellers like The Hunger Games or Fifty Shades of Grey can be picked up used, at a steep discount, on Amazon.com.