The foyer of the master's residence at Lowell House, the second oldest of Harvard's residential colleges, used to be home to countless portraits of Lowells, the wealthy Harvard family after whom the college is named. But when Diana Eck became master of Lowell House (with her partner Dorothy Austin) in 1998, those portraits got moved to a side room. Now students and other guests loitering in the halls are treated to a panorama of stunning pichhavais, devotional hangings from the temples of Krishna in Rajasthan. A great white cat arches its back against the spindly legs of a small, wooden table. On top of the table is the March 30 issue of Muslim Journal.

The change in the landscape, as it were, of the Lowell House front hall mirrors another change, one that Eck has spent the last decade of her life chronicling: the change in America's religious landscape. The fruit of her labors appears next month in A New Religious America: How a "Christian Country" Has Now Become the World's Most Religiously Diverse Nation (Harper San Francisco; Forecasts, May 28), a thoroughly researched and lovingly written ethnography that tells us, well, just what the subtitle promises. America is no longer a kingdom of WASPs—it now encompasses a full spectrum of faiths.

HSF couldn't be more excited about the book. John Loudon, Eck's editor, says, "Eck is refocusing the whole field to a new awareness that the world religions are no longer on the other side of the world, but thriving right in our own American neighborhoods. The old view of American religion as simply Protestant, Catholic and Jewish is as outdated as Ozzie and Harriet, even if the media, politicians and even academia are mostly blind to the new realities. Eck's book tells the big, untold story behind the remarkable new census figures." The publishers have big plans for the book, which was agented by Jill Kneerim at Palmer & Dodge. The initial print run is 50,000, and Eck will undertake an eight-city tour.

Eck is a scholar of Indian religions, though that's not what she set out to be when she headed to college in the 1960s. A Montana-born government major, she decided in her junior year of college that she wanted to go abroad. "But I didn't want to go to France or Spain, where all the Smith girls went," she says, chuckling. Spurning Paris, Eck headed to Banaras (now known as Varanasi), a Hindu holy city on the bank of the Ganges, and she says it changed her life. "I realized when I got there," she recalls, "that I wasn't all that interested in studying Indian government. But I was fascinated by Indian religion." In Banaras, she saw all sorts of people doing all sorts of religious things—but the Indians' rituals and prayers and beliefs were quite different from what she'd encountered as the church-going granddaughter of Swedish immigrants in Bozeman, Mont. Eck began to learn a little about the religious traditions of India, and she was hooked.

After receiving her doctorate from Harvard in 1976, Eck stayed on at the university as a professor of Indian religions. Circumstances conspired to turn her attention from India to America in the late 1980s. First, the World Council of Churches in Geneva asked her to help them think about inter-religious issues: who, after all, could be better suited for the task than a scholar of the East who also happened to be a Methodist laywoman? Eck undertook her WCC work with gusto, traveling around the world studying problems of religious pluralism. How were Protestants in India to deal with Hindu religious festivals? Should they participate or not? Should they shield their kids from the influences of another faith, or introduce them to Hindu ritual as part of their Indian heritage? "Those were the sorts of questions I was addressing on a global scale," says Eck, "and I suddenly realized that they were questions to be asked in my own country, too." In America, she says, interfaith councils had "suddenly started springing up like crocuses."

If her experiences in Geneva prodded Eck to think a little more about home, so did her experiences in the classroom. "The Immigration Act of 1965," she explains, "was suddenly being felt" in the hallowed halls of Harvard. With its passage, quotas limiting the influx of immigrants who hailed from anywhere other than western Europe were dropped: Asians, Africans and other migrants long denied entrance to America were, at least legally, welcome. "You don't feel that kind of change at first," says Eck. But by the late 1980s and early 1990s, the children of those immigrants were in college, turning up in Eck's classroom to learn about Hinduism. "I realized I would need to learn something about the next chapter of Indian religions: what was happening to these religions in my own neighborhood?"

To answer that question, Eck won a grant from the Lilly Foundation and established the Pluralism Project. She had three primary goals for the project. The first was simply to document the changes taking place in America's spiritual geography. Where were the Buddhist temples? The Muslim mosques? Who worshiped there? Second, Eck wanted to examine how those traditions were changing, how they were adapting to America. Congregationalists peering out of their steepled churches and watching the demographic and cultural transformation knew that the once-familiar Christian landscape was changing. But Buddhists and Hindus and Muslims were also changed by their move to the U.S. "The Hindu community in Nashville," she says, "came together to build a temple, and they encountered a level of diversity in their faith that many had never encountered in India, except as tourists." The same can be said of Buddhists and Muslims in America. "Today, American Islam spans a spectrum that Malcolm X had to go on hajj to discover." Finally, she wanted to think about how these religions were changing America.

From 1991 to 1993, Eck sent out a team of Harvard undergraduates to do summer research in their hometowns. They brought back dazzling reports of Buddhist zoning battles in Denver, Hindu summer camps in Pennsylvania. During the following academic year, students turned their field notes into seminar papers—and sometimes into published academic articles. In 1997, Eck and her team transformed their research into a CD-ROM, On Common Ground: World Religions in America. The project also produced a guide, World Religions in Boston, that covers the Jain Center of Greater Boston (its home is a former Swedish Lutheran Church in Norwood), the Sri Lakshmi Temple, Vipassana meditation centers in Cambridge and Barre, Sikh gurdwaras in Milford and Millis, and a Zoroastrian Association of Greater Boston, as well as the more familiar synagogues and churches.

The Pluralism Project's crowning jewel is Eck's new book; in many ways, the book is simply a fully fleshed out answer to the three questions Eck set out to ask 10 years ago. The central three chapters look at Buddhists, Hindus and Muslims in America, but Eck is also interested in how the rest of the country is responding to this huge demographic and cultural change.

The answer to that question, not surprisingly, is complicated. Many Americans are simply unaware that they have Hindu and Muslim neighbors. Others are overtly hostile. In a chapter pointedly called "Afraid of Ourselves," Eck claims, "American xenophobia has given rise to a thousand stories of insult and insinuation, assault and hatred." She recalls a Fourth of July op-ed piece she wrote a few years ago for the Los Angeles Times. In it, she described the many places the American flag was flying that July Fourth—"on the grand staircase of the His Lai Buddhist Temple in Hacienda Heights, Calif., for example, or next to the blackboard in the fourth-grade classroom of an Islamic school in Orange County." A man in Tampa, Fla., saw the editorial and wrote in response: "If this is indeed the case... then I wonder how all these people got here.... Now it is time to close the doors. I suggest they go back where they came from."

The United States, Eck contends, is in the process of a cultural change the likes of which we've never seen before. "It is massive," she says, "and it has religious dimensions. This is not just a few gurus coming over in the 1970s. This change is here to stay, and it can't be dismissed by saying simply that there are more Southern Baptists than Hindus. It is not a matter of numbers, but of a basic transformation of our religious society." We need, says Eck, to be able to hear a variety of religious voices and hold in our mind's eye a religious landscape that is very different from the homogenous swath of Protestantism that we imagine stretching from New England's Puritan churches to California's Crystal Cathedral.

The struggle around religious diversity, she predicts, may be the most important battle in the American public square in the next few decades. "We're on an upswing," she says, "in recognizing religious diversity." Ironically, she says, it took the issue of faith-based communities receiving government funding to help Protestants, Catholics and Jews to realize that America included worshippers other than Protestants, Catholics, and Jews. "When it became clear that Hindus and Muslims might receive funding for faith-based initiatives, there was a certain alarm."

Eck, perhaps revealing her roots in the civil rights movement, is careful to hedge: "Religion isn't going to replace race as a central issue," she says. But discussions of sameness and difference, of prejudice and exclusion, "just can't go on the same way." In the rash of black church burnings, Eck reminds us, "there was also a destruction of mosques, and that can't be thought of entirely in terms of race. There is an otherness to a mosque that has to do with religion—that has to do with Islam."

Vandals and nativists notwithstanding, Eck exudes optimism. She knows that there are many folks out there like her correspondent from Tampa, and she knows that adjusting to the sea changes America is experiencing is no small task. "It could," she admits, "lead to greater tension and fragmentation." But America's increasing religious diversity, she insists, can be a blessing, not a bane.

Eck seems faintly relieved to be finished with A New Religious America. When she applied for her first Lilly grant, she didn't imagine she'd still be in the midst of studying America a decade later. She is eager to turn to her next project, a study of pilgrimage networks and sacred geography in India. But even if Eck's next book returns to India, she hopes to see "more books that reach out to a wide audience, telling us about the different religious traditions that now are flourishing in America." Eck's dream projects? She wants to see books by Muslim Americans about their experience of Islam in America. "I want Salam Al-Marayati of the Muslim Public Affairs Council to write about what it means to be a Muslim in America, and I want similar books from Hindus." And she fantasizes about Christian books, too.

With a wicked gleam in her eye, she says, "I'd like to see a book by a Southern Baptist theologian addressing questions of neighborliness. I want a good Southern Baptist theology that would think about neighbors in a world of many faiths." Eck is on a roll; too bad she's a mainline Methodist and can't write this book herself. "I want it to break from the Southern Baptist focus on the family and think about a category that is far more salient in the New Testament: strangers and neighbors."

America is a land of tremendous religious diversity; that much is clear. The question, says Eck, is what we do with diversity. "You can rest in a sort of laissez-faire toleration of it, and that will probably lead to social fragmentation." Or we can engage it so that it becomes a source for answering the very questions that bedevil us. "There is real strength in the process of getting to know people," says Eck. "It is one thing for the Southern Baptists to say there are nine million Hindus in India lost in the darkness of their polytheism. It is another thing for them to meet two or three Hindus who live across the street from them in Houston." Indeed, if one were to sum up Eck's project in a word, one might choose not pluralism, with its resonances of academia and punditry, but neighborliness.

Winner is a freelance writer based in New York.