The Tunguska Mystery (Astronomers' Universe)
"This  is arguably the best book you will find on this subject - thorough,  balanced, detailed, in-depth and very well-written on top of everything  else. If you're interested in the Tunguska mystery, start here. My hat  is off to Rubtsov for his scholarship and lucid writing style." Michael  Schmicker, "Journal of Scientific Exploration"