With his family’s communist leanings on one side and lapsed German Reform Judaism on the other, Mark Oppenheimer says, “I like to think I was uniquely bred to be non-religious.”

In fact, his freshman year at Yale was the first time he ever attended High Holy Day services.

Which makes it all the more remarkable that Oppenheimer not only obtained a Ph.D. in the history of American religion and is writing about a religious rite for his second book, but that he is the first winner of the Koret Young Writer on Jewish Themes Award.

Winning the award brought Oppenheimer, 29, of New Haven, Conn., to Stanford University, where he has been teaching a course on American Jewish fiction. He will be speaking Thursday, Dec. 4 in San Francisco.

So how did someone who grew up in the predominantly Catholic milieu of Springfield, Mass., and who attended a mostly Protestant prep school, find his way to Judaism?

The serious answer: When he was in college, for the first time, Oppenheimer met people who were seriously engaged in Judaism. But there’s a less-serious answer, too. A friend said he should go to Yale’s first-ever Reform High Holy Day services because the woman leading them was hot.

Oppenheimer called it “transformational.” That a young woman would be leading services “was not something my perception of Judaism would have permitted,” he said.

Slowly, Oppenheimer found himself not only studying religion, but becoming an active participant in his own.

In “Knocking on Heaven’s Door: American Religion in the Age of Counterculture,” Oppenheimer examines how the social movements of the ’60s impacted several sects of Christianity as well as Judaism.

While he discusses gay rights in relation to the Unitarians and feminism’s influence on the Episcopalians, his chapter on Judaism focuses on the birth of the chavurah — small groups of Jews who generally meet at someone’s home to worship — which originated within the Reconstructionist movement.

Oppenheimer chose an exclusively Jewish topic for his second, which is in progress. Tentatively called “At Thirteen,” the book, which will be published by Farrar Straus and Giroux next year, is an examination of the bar mitzvah and the role it plays in the cultural life of American Jews.

Though Oppenheimer never became a bar mitzvah himself, the subject appealed to him on a number of levels. He was intrigued by the religiosity of children, since “a lot of the most interesting spiritual people are kids,” he said. “They’re often more spiritual than their parents.”

He found a vast difference between New York b’nai mitzvah and those in rural places, where families celebrated the ritual even if they couldn’t afford a catered meal, or there was no caterer nearby to do it.

Oppenheimer attended a Renewal affair in Arkansas and a Chassidic one in Alaska. He attended a celebration of two adult Jews-by-choice.

He was surprised to learn that “the Lubavitch kid had the biggest party of all, and it was the most spiritually meaningful.”

Oppenheimer expressed a certain awe of Lubavitch kids, who take on full responsibilities of adulthood at 13, as opposed to their Reform and Conservative counterparts, and can sight-read Torah and know trope by heart.

“What was I doing at that age?” he mused, “watching a lot of ‘Brady Bunch’?”

But Oppenheimer didn’t stop with interviewing the kids and their families. “There’s a whole economy that exists around this,” he said, “with the klezmer musicians, the DJs, the florists, the caterers, the rabbis, the tutors,” etc.

While much has been written about how the party can sometimes overshadow the ceremony, Oppenheimer said he found the opposite to be true.

“The kids didn’t want to talk about their parties. They wanted to talk about their speech or their Torah portion.”

“Knocking on Heaven’s Door: American Religion in the Age of Counterculture” by Mark Oppenheimer (284 pages, Yale University Press, $30).

Mark Oppenheimer will join Don Lattin, San Francisco Chronicle religion writer, at 7 p.m. Thursday, Dec. 4, at A Clean Well-Lighted Place for Books, 601 Van Ness Ave., S.F., in a talk co-sponsored by the Koret Foundation and the San Francisco Jewish Community Center. Information: (415) 292-1219.