In this fascinating exposé, investigative journalist Katherine Stewart uncovers what she asserts to be the hard truth about the Christian right's "stealth assault on America's children." In "The Good News Club" (Public Affairs, 304 pages, $25.99), she investigates crusading evangelical religious missions disguised as innocuous after-school programs, beginning with one at the public elementary school where her children were enrolled in Santa Barbara, Calif.

Stewart first encountered a Bible study class called the "Good News Club" in January 2009. To her alarm, the course -- while voluntary -- was actively (and often without notice) breaching the separation of state and church.

Part of a wider initiative orchestrated by the Child Evangelism Fellowship, the class was designed to reconstruct America's public school system as an evangelical Christian institution. Its object, Stewart found, is to indoctrinate youngsters in the belief that their school favors the Christian faith.

Perhaps her most surprising revelation is that, by the end of 2010, Stewart counted nearly 3,500 similar groups, from small-town America to major cities like Seattle and New York. These schools house and profit from church-funded religious groups that are willing to pay to borrow their classrooms.

Stewart's analysis suggests that fundamentalist Christianity has amassed undue influence in what should remain an inviolably nonreligious educational endeavor.

Stewart has dug deep, interviewing both proponents and detractors of religiously centered education, including school board members, superintendents, local club leaders, students and athletic directors who have "turned [sports programs] into religious recruiting," according to Stewart.

She describes how such a club wins schoolwide access, even against the opposition of a district superintendent. Each religious sect is armed with legal papers, an instruction manual on "how to incentivize unchurched children to attend meetings," and behind-the-scenes support from the Child Evangelism Fellowship.

"As I flip through the hundreds of pages of THE PLAN and its supporting materials," Stewart writes, "it becomes clear to me just what kind of corporation the CEF is most like: it's a nonprofit, religious version of a multilevel marketing corporation. ... The local Clubs in turn provide the manpower and the money."

These same efforts, Stewart concludes, deprive public schools funding in favor of vouchers for enrollment in religious-affiliated private institutions. While voicing earnest concerns about the Christian right's influence on public education, Stewart is a gracious narrator, respectful of the religious and nonreligious participants she came across during her quite vast research.

In sum, the book is an important work that reveals a movement little discussed in the mainstream media, one Stewart worries is poised to damage "a society as open and pluralistic as ours."

Alexander Heffner is a freelance writer whose work has appeared in the Washington Post, Boston Globe and USA Today.