In his far-ranging and detailed history, Kurlansky defines the various ways people of different times and cultural contexts have related to salt as both flavoring agent and preservative. While salt's role as a seasoning is easy to understand—with salt and salt-based sauces continuing to be primary methods of seasoning in a variety of modern cuisines—it can be easy to forget salt's role in preservation due to our heavy reliance on freezing and refrigeration as means of preservation. Kurlansky reminds readers of the various forms of salt-based preservation that have been crucial for preserving foods throughout known history, including salting meats, pickling foods, and other methods. Preserving food is a key part of maintaining food access and quality of life during times when food cannot be readily harvested, and thus salt can understandably be tied to social stability—or the lack thereof.

Kurlansky investigates the ways in which salt has contributed to the rise and fall of empires and the toppling of oppressive regimes. Kurlansky notes that salt is incredibly plentiful, especially in coastal and coastal-adjacent areas, due to how easily it can be obtained from seawater. Despite this, ruling powers have often taxed salt heavily or otherwise worked to make it a scarce commodity, leading to it being used as a form of currency in various times. This clearly shows the way in which regimes will regularly create artificial scarcities and inequalities in order to establish means of social control—and how these can backfire and lead to revolt, such as anti-colonial activity in India centered around salt.

Through his broad history of salt, Kurlansky also traces the ways in which a common ingredient central to human life is treated similarly and differently across various times and cultures, as well as the way cross-cultural interaction and trade are central to the way salt is present in our daily lives. Kurlansky uses this history to give us new context for culinary staples that are all around us.