<human>:  What books and films have had the biggest influence on pop culture in the last 20 years?
<bot>: The two books and films that have had the biggest influence on pop culture in the last 20 years are The Lord of the Rings trilogy and the Harry Potter series for books, and The Avengers and Avatar for films. All of these works have become iconic within popular culture, influencing everything from fashion to music to TV shows.