“Spiritual but not religious.” So many Americans describe their belief system this way that pollsters now give the phrase its own category on questionnaires. In the 2012 survey by the Pew Religion and Public Life Project, nearly a fifth of those polled said that they were not religiously affiliated — and nearly 37 percent of that group said they were “spiritual” but not “religious.” It was 7 percent of all Americans, a bigger group than atheists, and way bigger than Jews, Muslims or Episcopalians.

Unsurprisingly, the S.B.N.R.s, as this growing group is often called, are attracting a lot of attention. Four recent books offer perspectives on these Americans who seem to want some connection to the divine, but who don’t feel affiliated with traditional religion. There’s the minister who wants to woo them, two scholars who want to understand them and the psychotherapist who wants to help them.

The Rev. Lillian Daniel’s book “When ‘Spiritual But Not Religious’ Is Not Enough” (Jericho, 2013) began as a short essay for The Huffington Post, in which she voiced her exasperation with the predictability that she found in spiritual but not religious people.

“On airplanes,” Ms. Daniel wrote in the essay, in 2011, “I dread the conversation with the person who finds out I am a minister and wants to use the flight time to explain to me that he is ‘spiritual but not religious.’ Such a person will always share this as if it is some kind of daring insight, unique to him, bold in its rebellion against the religious status quo.” Before you know it, “he’s telling me that he finds God in the sunsets.”