It's the elephant in the family room, and it's getting bigger. Each year, among 2.3 million American unions, thousands of Catholics marry Protestants, Jews marry Christians, and Buddhists, Mormons, Muslims and Greek Orthodox believers marry someone from another religion.

Yet not a lot is written about this phenomenon. The institutions of religion normally charged with marrying couples don't encourage the practice. In Judaism, where the rate of intermarriage is especially striking—an estimated 50% of marriages among Jews today are interfaith—it's even difficult to find a rabbi who will conduct a ceremony. In the American Jewish community, "there are few people who are comfortable writing about it in a nonjudgmental, helpful way," says Stuart Matlins, publisher at Jewish Lights, which has published two recent books on interfaith marriage and family. "People in positions of authority within the Jewish community do not want to appear to be encouraging it."

Mary Helene Rosenbaum, executive director of Dovetail Institute for Interfaith Family Resources and a practicing Catholic married for 40 years to a professor of Judaic studies, puts it more bluntly. "I can't tell you how many times some bright young program director will call and book us, and when the plan to invite us percolates up, this person is going to call back and say, 'They don't want you,' " she says. (Rosenbaum said Dovetail is "radioactive" in the Jewish community because it does not push intermarrying couples toward the raise-your-kids-Jewish option.) The organization has a publishing arm offering such titles as The Interfaith Family Guidebook: Practical Advice for Jewish and Christian Partners (1998) by organization founder Joan Hawxhurst.

The state of publishing on this topic reflects this climate: a few books emerge each season, and the best live on as backlist resources. Publishers and authors know they are meeting a perennial, unsanctioned and growing need.

Rev. Susanna Stefanachi Macomb, author of Joining Hands and Hearts: Interfaith, Intercultural Wedding Celebrations—A Practical Guide for Couples (Fireside, Jan.) gets calls from couples and clergy all over the world. "I got a phone call from a rabbi in Costa Rica. He was doing a wedding for a friend's daughter who was marrying a Muslim, and he wanted to know how to incorporate Muslim elements into the ceremony," says Macomb.

Her book stakes out this cutting edge, going beyond Jewish-Christian relationships to address the new unions of traditions, cultures and religions now being forged by people in their 20s and 30s. A licensed and ordained interfaith minister since 1996, Macomb has performed weddings in one of the country's multicultural epicenters, New York City. She had three publishers bid in a week's time on the book, her first, done in collaboration with writer Andrea Thompson. The book is intended for both couples and clergy, with a questionnaire for the couple, chapters on ceremonies and customs from a range of religions and cultures, and the stories of and ceremonies designed by eight couples.

Marcia Burch, v-p and director of publicity at Fireside, hopes the book will be prominently featured among the wedding books stores will highlight come spring. Since the market includes not just couples but also clergy, publicity is being aimed at religion publications and seminaries as well. Macomb has been speaking on the topic at seminaries and running out of books at those engagements, "whether we bring 20, 30 or 40," she notes.

Making a Successful Jewish Interfaith Marriage by Rabbi Kerry M. Olitzky with Joan Peterson Littman (Jewish Lights, Feb.) focuses on intermarriage from a Jewish perspective, offering what is billed as "straightforward and nonjudgmental advice." Olitzky, executive director of the Jewish Outreach Institute and a prolific author, maintains that intermarriage offers an opportunity to increase the Jewish population if more intermarried couples are welcomed and encouraged to raise their children in Judaism. Between two-thirds and three-quarters of such intermarried households don't choose that for their children. In the same vein, Jewish Lights also published The Guide to Jewish Interfaith Family Life: An Handbook, edited by Ronnie Friedland and Edmund Case (2001), drawn from the titular Web site of resources for intermarried Jewish families.

Within American Christianity, interchurch marriages crossing denominational lines are also common and under-acknowledged. United in Heart, Divide in Faith: A Guide for Catholic-Protestant Couples (SunCreek, Apr.) by Sandra L. Stanko, a partner in a mixed-Christian marriage, addresses that phenomenon, targeting couples beginning relationships in addition to those committed enough to plan marriage. SunCreek is an ecumenical Christian imprint of Texas-based Catholic publisher Thomas More. "There was a need for resources for those couples from both perspectives," says SunCreek acquisitions and marketing director Debra Hampton. The book will be distributed in both the CBA and general markets. One major chain buyer told her, " "There's nothing quite like this on the market," Hampton reports.

Demographic projections show this niche growing as the country's ethnic and religious diversity offers more chances for relationship partners to cross paths, cultures and faiths in new ways. Author Macomb sees this mixing as a norm among the young people she marries, who are so used to cultural and religious variety they don't even begin to consider a potential for conflict. "When they're young and you talk about conflict in terms of religion and race," she says, "they look at you as if you're Martian."