This encyclopedia contains individual histories of each of the nearly 100 World's Fairs and expositions held in more than 20 countries since 1851. This is a thorough revision and updating of the book originally published as A Historical Dictionary of World's Fairs and Expositions in 1990. The new entries include essays on the world's fairs to be held in Zaragoza, Spain, in 2008 and in Shanghai, China, in 2010. Many of the original essays have been revised and expanded. Topics covered include goods, tourism, nationalistic competition, architecture, art and culture, and "exhibition fatigue."

Each fair history has its own annotated bibliography which provides, when possible, the location of relevant primary sources and comments on the quality of secondary sources. Appendices cover the Bureau of International Expositions, fair statistics, fair officials, fairs that did not qualify for inclusion, and fairs that were planned but never held. The book includes a foreword (and appendix) by Vicente Gonzalez Loscertales, the secretary general of the Bureau of International Expositions.