Though variations of the subtitle "What would Jesus do" have been used by Christians for centuries as a form of imitatio dei, the imitation of God, it gained much greater currency following publication of the book.

In His Steps takes place in the railroad town of Raymond, probably located in the eastern U.S.A. The main character is the Rev. Henry Maxwell, pastor of the First Church of Raymond, who challenges his congregation to not do anything for a whole year without first asking: “What Would Jesus Do?” Other characters include Ed Norman, senior editor of the Raymond Daily Newspaper, Rachel Winslow, a talented singer, and Virginia Page, an heiress.

The novel begins on a Friday morning when a man out of work (later identified as Jack Manning) appears at the front door of Henry Maxwell while the latter is preparing for that Sunday’s upcoming sermon. Maxwell listens to the man’s helpless plea briefly before brushing him away and closing the door. The same man appears in church at the end of the Sunday sermon, walks up to “the open space in front of the pulpit,” and faces the people. No one stops him. He quietly but frankly confronts the congregation—“I’m not complaining; just stating facts.”—about their compassion, or apathetic lack thereof, for the jobless like him in Raymond. Upon finishing his address to the congregation, he collapses, and dies a few days later.

That next Sunday, Henry Maxwell, deeply moved by the events of the past week, presents a challenge to his congregation: “Do not do anything without first asking, ‘What would Jesus do?’” This challenge is the theme of the novel and is the driving force of the plot. From this point on, the rest of the novel consists of certain episodes that focus on individual characters as their lives are transformed by the challenge. Source: Wikipedia