The much-dissected Pew Research Center study of 2013, "A Portrait of Jewish Americans," revealed that most U.S. Jews locate their Jewishness in their ancestry and culture--not in religion. Abigail Pogrebin wondered if perhaps that's because we haven't all looked at religion closely enough. Although she grew up following some holiday rituals, Pogrebin realized how little she knew about their foundational purpose and current relevance. She wanted to...