Growing up in England, John Reader consumed potatoes at almost every meal -- with roast meat on Sundays, with slices of cold meat on Mondays, with shepherd's pie on Tuesdays. As he notes, the regularity allowed him "to take potatoes for granted ... as an unassuming item of food that was plentiful enough to eat daily and might occasionally bulk up a meal whose major attraction was in short supply."

Later, quite unexpectedly, Reader, a writer/photojournalist/professor, became fascinated by potatoes not so much as food to consume but as a window on the conditions of entire societies, from Peru to Papua New Guinea to Ireland. Now, in the tradition of so many previous books about specific edibles (salt, cod, pizza), Reader has written an entire book about potatoes in their astonishing variety -- "Potato: A History of the Propitious Esculent."

The subtitle is meant both ironically ("propitious esculent" is a grand phrase describing something thought of as so plain) and respectfully (they feed the world -- "esculent" means "edible plant" -- while providing first-rate nutrition).

Reader's book is not the first devoted to potatoes; the bibliography shows predecessors, which he gratefully acknowledges, but for now, it holds sway. Those in the Twin Cities and other parts of the United States might feel disappointed if they are focused more at home than the rest of the world; Reader barely mentions potato growth and consumption in the USA -- not even Idaho.

As expected of an author from the British Isles, he does devote many pages to the role of the potato in Ireland, where it became the victim of diseases starting in the 1840s, leading an entire nation to face famine. That story is well known, but other stories in the book are hardly known at all, starting with the invention, if you will, in Peru of potatoes as a staple food. That story goes back about 8,000 years. Later, at the close of the 16th century, Spanish explorers who conquered portions of South America transported potatoes to Europe.

Many authors tend to give too much weight to their subjects as fascination (perhaps obsession) grows during research. Reader could be accused of falling into that trap. Still, when he writes that "the potato changed world history," the evidence he has marshaled seems mighty convincing.

Steve Weinberg is a biographer in Columbia, Mo.