On a cool summer evening in the desert between Taos and Santa Fe, two women lean on pillows, sip coffee, and discuss their past. One is a professor of history and gender studies and has been a feminist and an agnostic throughout most of her adult life. The other is a devout Muslim of the mystical Sufi order. What brings two such different women together? Attending high school in 1950s suburban Los Angeles, Lois Banner and Fran Huneke had been best friends, with their minds on books and boys. But while Banner became an academic feminist, Fran converted to Islam and moved to Egypt. Forty years...