Mainline vitality.

Christianity for the Rest of Us: How the Neighborhood Church is Transforming the Faith, by Diana Butler Bass. HarperSanFrancisco.

Liberal churches are dying. Conservative churches are growing. Everyone knows that's true. Except that it isn't.

So argues Diana Butler Bass, a former college professor, syndicated columnist, trained historian, and sociologist. The Lilly Endowment has funded her multiyear exploration of mainline churches that are readapting ancient Christian practices for a new day. This is the third installment of a trilogy of books about these churches presenting Buffer Bass's research, and it is a gem.

The unfortunate implication of Dean Kelley's thesis in Why Conservative Churches Are Growing, first published in 1972 and rehashed often since, was that only conservative churches can grow. It only takes one exception to disprove the rule, and Butler Bass has hundreds, She studied dozens of mainline congregations carefully, and 10 intensely, attending so often she would be asked when she was going to turn in her pledge card. "Real people in real churches taught me by sharing their stories," she writes, and she is wise to let them have their say.

The book also takes aim at the secular press's tendency to assume the Religious Right's claim that only it speaks for true, vibrant religious communities. When asked what she was writing about, Butler Bass would respond "The other Christians. The ones you don't hear about in the media. The quiet ones."

A particularly strong chapter describes a visit to her old neighborhood in Baltimore and her home church, St. John's United Methodist. If there is anything to the charge that mainline churches fail to grow, it is this: We mainliners simply failed to adapt quickly as old neighborhood patterns changed. The pattern of life in Baltimore's ethnic enclaves was not substantially different in 1959 than it had been in 1900. But that world died. St. John's Church almost has as well. But it took a while for anyone to notice. Liberal churches often carried on for decades in a sort of joyless version of Rotary--without intentionality about prayer, the passing on of the faith, or exuberant worship--as shells of their former selves. Those that have reversed the decay have essentially recreated within their walls the lost villages of the sort in which Butler Bass grew up. "The whole thing feels like a village square--church, children, and cafe--around the water fountain in the middle of suburbia," she writes.

BUTLER BASS organizes the heart of the book around 10 "signposts" of renewal ancient practices reappropriated by the churches in ways that are sensitive to their local contexts. The book's greatest moments come in telling of these practices with specific names, places, and histories included. These churches have plugged their leaks with intentionality about the life of the Spirit. They successfully link the progressive politics of their heritage with the enthusiasm of their evangelical brothers and sisters, without the narrow vision or exclusive politics. They have taken up the practice of public testimony by lay people dining their services, They teach theology with rigorous catechetical programs. They find ways to incorporate things such as "diversity" and "beauty" into church practices so that they are actively pursued in programming and celebrated liturgically. They practice justice--not by sending money to needy people far away but by becoming their friends and inviting the homeless to pitch tents on the church lawns. Butler Bass marvels that many suburbanites feel great kinship with the homeless they serve: They are homeless too, spiritually speaking.

The book charts these wanderers' transformation from nomads to pilgrims on a raucous story-telling communal journey of faith. Butler Bass spies here a certain "liturgical politics"--a radical middle of sorts, neglected by politicians and the media, in which churches engage the civic powers as political agents for the common good in ways far different than the Religious Right.

It is a shame to find any fault with a book so brilliant, but the line between mainliners and evangelicals or Catholics feels a bit too brightly drawn for me. Many mainliners are also evangelical, and many Catholics and evangelicals also strive to be as "committed but not exclusive" as the churches detailed. I sense here pressure to write for a general audience that does not leave space for nuance.

Surely we liberals have to be open--even to those who are closed to us--if charity is to trump exclusivity. That's a quality that marks this rare book, which actually deserves the overused adjective "important."

Jason Byassee is assistant editor at The Christian Century and author of Beading Augustine: A Guide to the Confessions (Cascade Books, 2006).