The cost of a book of stamps can vary depending on where you purchase it, but as of the most recent updates, a book of 20 first-class stamps in the U.S. usually costs around $12.80. Prices can change, so it's always a good idea to check with your local postal service for the most accurate information. Are you mailing something special, or do you often find yourself needing stamps for various occasions? I'm curious to know more about your mailing habits!