This popular science book examines 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. 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.