Her book comes at a challenging time for church life in America. Many denominations are steadily losing members. More and more people aren't affiliating with any religion, including a third of those born between 1980 and 2000—"the single most common religious identity among this generation," according to the Public Religion Research Institute.

But more importantly, "Christianity is losing a little bit of its death grip over the culture," Evans said. Sliding numbers, along with cultural and political battles over issues like same-sex marriage, have helped cultivate a sense of persecution or defensiveness among some Christians. "There’s a sense that the culture is shifting," she said. "That can be fearful for some people."

The interesting thing about this, though, is that an overwhelming majority of Americans still identify as Christians—roughly 75 percent. Church life is still very much part of American life, which is why the frame of Evans's book is so useful. She writes of growing up in an evangelical congregation in Tennessee, quitting church in her twenties, planting and closing a new church before she turned 30, and finally settling into an Episcopalian congregation—for now—at 33. Hers is a first-person account of what it's like to struggle with the existence of God and hate church politics and still yearn, a little or a lot, for the kind of community that religious worship can bring. After she and her husband decided to leave Grace Bible Church, the congregation Held grew up in, over the issue of same-sex marriage, "I put my head in my hands and cried, startled to tears by the selfishness of my own thoughts," she wrote. "Who will bring us casseroles when we have a baby?"

Many Millennials may not go to church, but like Evans, they have a church story. These stories don't come out in demographic data, which obscures an experience that a lot of young Americans probably have: "No one really teaches you how to grieve the loss of your faith. You're on your own for that," Evans writes. For those who are trying to figure out where they fit, she just doesn't believe that punk-rock Christianity will do the trick of getting people back in the pews.

"The reasons Millennials are leaving are more complex than a lack of cool," she said in an interview. "We’ve been advertised to our entire lives. We can smell B.S. from a mile away. So if you’re just trying to sell us a product, we can tell.”

Although Evans's book is not directly about Millennials leaving the church, she talks a lot about that topic, for she is a Millennial who once left the church. She gives some credence to the cultural shifts that have made certain theological concepts difficult to parse in public—as she puts it, "I'm as uncomfortable as the next Honda-driving, NPR-listening, New York Times-reading progressive with the notion of exorcising demons." She also takes issue with the gender politics in certain parts of the church; with Mars Hill, for example, "the exterior was hip and edgy, but they made the old mistake of authoritarian leadership," she said in an interview.