You can now buy the recently released book, Fall of a Thousand Suns: How Near Misses and Comet Impacts affected the Religious Beliefs of our Ancestors. It is available through iBooks and Amazon.
This website only lists information on modern-day comets and meteor showers. The book, however, thoroughly investigates how specific ancient impacts and near misses changed religious beliefs around the world.
The Discovery of Comet Hyakutake
On March 25th, 1996, Comet Hyakutake passed .1 AU from Earth— closer than any comet in the past 200 years. The frighteningly thing is that this comet had been discovered less than two months earlier by an amateur astronomer with a pair of binoculars.