Elaine Khosrova never intended to write an entire book on butter. A former pastry chef and food writer, her first exposure to butter’s wide-ranging properties came when she was assigned to a butter tasting. “I hadn’t expected to experience such a range of color, flavor and texture among the 12 or so samples,” she recalls. “Knowing butter is essentially made from a simple process of agitation using just one ingredient—cream—I couldn’t account for why there was such variation.”

Khosrova already had a soft spot for dairy; she’d founded a specialty cheese magazine in 2008. But butter was unplumbed terrain for her, and as she began to delve deeper, she realized that its cultural legacy had been overlooked in culinary literature, too. She began work on Butter: A Rich...