Similar to the list of books That Changed The World is this list of mono-histories, biographies of singular items.
Salt: a world history, by Mark Kurlansky - Published in 2002, Kurlansky's history of the world's most important commodity is probably the best known mono-history and the only one to appear on the best-seller lists. I found it fascinating and inspiring. Kurlansky must have enjoyed his foray into mono-history because he's followed up on Salt with Cod: A Biography of the Fish That Changed the World and The Big Oyster: History on the Half Shell.
Other topics covered by these books are pizza, pencils, and the alphabet. (via rebecca's pocket (welcome back!))
Update: Several people have noted that Cod was published five years before Salt. (thx, all)