While some vacationers immerse themselves in potboilers like The Da Vinci Code this summer, President Bush has been spending his downtime with something a little less sizzling: a book about the history of salt.

The Los Angeles Times recently reported that Bush took three books with him on his Crawford, Texas, retreat, including Salt: A World History, by Mark Kurlansky. While some might think the topic is a strange diversion in these trying times, it's more relevant than you might think.

"The analogies between salt and oil are striking," writes Times reporter Warren Vieth.

"For most of recorded history, salt was synonymous with wealth. It established trade routes and cities. Adventurers searched for it. Merchants hoarded it. Governments taxed it. Nations went to war over it.

"More than four centuries ago, Queen Elizabeth I warned of England's growing dependence on foreign salt. France's salt tax, the gabelle, was one of the grievances that gave rise to the Revolution of 1789."

The book is no breezy read, to be sure. And the other two titles are equally serious: Alexander II: The Last Great Tsar, by Edvard Radzinsky, and The Great Influenza: The Epic Story of the Deadliest Plague in History, by John M. Barry.

Why these two? Author Barry told the Times he had been consulted by the Bush administration on the flu epidemic of 1918 in order to help it avoid another flu disaster. As for Alexander II, apparently the ruler fought his own form of terrorism - a subject Bush would obviously find important.

In all, it's a reading selection you're not likely to find at your average beach. Meanwhile, there's no word on whether the president has plans for The Da Vinci Code.