We experience networks every day: networks of friends, communication, computers, the Web, and transportation. The networks in our brain and cells determine our very survival. A First Course in Network Science (Cambridge University Press, 2020) is a textbook designed to introduce networks to a broad audience of undergraduate students from information science, computing, business, natural and social sciences. This book uses a hands-on approach: programming tutorials, exercises, and datasets allow readers to gain and test their understanding by building and analyzing networks in many domains. This talk overviews the book's topics, with a focus on cases that illustrate how networks help us understand our vulnerability to manipulation and misinformation on social media.