Four authors from the Combustive Motor Corporation, a New York-based artist collaborative, journey through the streets and alleys of New York City in search of works by UFO, ""one of the city's most elusive and prolific graffiti artists,"" famous for a ubiquitous, deceptively simple glyph: a balloon-headed extraterrestrial riding in a flying saucer. What they find goes far beyond the confines of cheeky vandalism or artist monograph; this illustrated volume also unearths historic evidence of extraterrestrial sightings in the far-flung corners of the world, from ancient paintings in antipodal caves, to Los Angeles street art from the early 1940s. The basic image of the alien is constant: a round head with beady eyes; thin arms and torso; and a saucer-shaped rocket-ship propelled by flickering flames. Like expert sleuths, the authors analyze each specimen, identifying commonalties in color, symmetry, material and surface. Included are photos of the art and the investigation, reproduced notes, a pull-out ""Field Guide to UFO Classification,"" and letters from the authors to such thinkers and artists as Stephen Hawking, Darryl McCray and David Bowie. No answers are provided, but the imagery is provocative and the scope of artistic and scientific inquiry is stunning-appealing to math and religion, to aboriginal dreams and shamans, to Tesla and Jung-the results of which make for compulsive page-flipping and disquieting rumination.