Book excerpt: This popular science book shares the fascination of the Tungus Event, a major mystery of the 20th century, in a factual and informed way. It provides "on-the-ground" descriptions of the site and explains the findings and the puzzlement of international scientists who have investigated it over the decades. After a brief and readable overview of comets, meteors, the sun and the solar system, the author ponders the range of possible explanations for the "great Siberian meteorite." The research is up to date, factual and scientific. While making no absurd claims to solving the puzzle, the author studies some intriguing clues in NASA's orbit diagrams for Comet Encke, and he is bold in discussing the possible causes of what was the greatest natural explosion in recorded history. As he points out, [Hypotheses] include rogue asteroids, mini black holes and even alien intervention....These explanations are not entirely equal to the facts. In the unique case of the Tunguska event, there was wholesale destruction to the mighty taiga woodlands but none of the debris that one would expect should exist from the body itself. Evidence like a strewn field of meteorite debris or meteoric dust on the trees and ground were never found, nor were any craters, in the area beneath the site of the fireball nor anywhere along the path it took. There are no craters because the Tunguska Cosmic Body (TCB) did not hit the ground. Atmospheric anomalies prior to the dramatic appearance of the fiery body puzzlingly occurred for several days, adding to the enigma. There are just a handful of English-language books on this subject. The most recent, The Tunguska Mystery, by the Russian Rubstov (Astronomers Universe, Springer Science 2009) is authoritative but highly technical and hard going for the general reader. Mr. Engledew instead tells the story in a balanced and engaging style.