The classic UFO-shaped like a flying saucer with a dome on top--in reality represents but a small fraction of the mystery aerial objects people have reported seeing over the past half century or so. Eyewitnesses around the world actually describe a bewildering array of forms in flight.

Here, for the first time, is a comprehensive look at the physical structure of UFOs, a book devoted to identifying and categorizing the dozens of different shapes the UFO phenomenon exhibits globally. From double-ringed to triange-shaped UFOs, from saucers to cigar-shaped craft-and more-this book documents each variant, describes often extraordinary encounters, and even takes the extra step of offering the skeptic's explanation for some of the sightnings.

What can the shape of a UFO tell us? In some cases, the shape of the object or phenomenon provides a strong clue to its origin. But in all cases, the classification system developed in this book shows quite clearly that there is no single solution to the UFO mystery--there are most likely many answers. And some surprises too.

Dennis Stacy was the editor of the monthly Mufon UFO Journal from 1985 to 1997. He received the 1995 Donald E. Keyhoe Journalism Award for a six-part series on UFOs that appeared in Omni. He is also the author of The Marfa Lights: A Viewer's Guide, and, most recently, he coedited UFOs 1947-1997: Fifty Years of Flying Saucers with Hilary Evans.

Patrick Huyghe is a journalist and editor of the The Anomalist, a journal that explores the mysteries of science, nature, and history. His articles have appeared in many publications, including the New York Times . He lives in Putnam Valley, New York.