Why is religion so widespread? Why do individuals donate large amounts of time, money, and effort to religious groups? What forms does the religious competition take? Why are individuals more religious in some countries than others? What is the future of religion? This book provides a non-technical introduction to how the economic approach answers these and other questions about religion. It defines the economic approach to religion and demonstrates how it is used to study a variety of religious decisions. It explains how religious groups confront credibility, free-rider, and coordination problems that challenge the collective production of religious goods and services. It also examines competition and regulation in religious markets around the world, how religious beliefs and preferences are transmitted and sustained, how religion likely emerged in humankind's distant past, and what the future of religion may hold. The book thus demonstrates how the tools and methods of economics provide fresh insight into a variety of religious behaviors. This book is intended for a wide audience in and out of economics. Though not a textbook per se, its discussion questions and suggested readings at the end of each chapter allow for easy incorporation into the classroom. The mathematics and statistics used by researchers are generally avoided. Both theory and evidence are presented, but the focus is on the ideas that provide a coherent conceptual framework that grounds a deeper exploration of the theoretical and empirical research in the economics of religion.