The UFO Experience

The book that introduced the world to Close Encounters of the First, Second, and Third Kind. J. Allen Hynek — astronomer, former US Air Force UFO consultant, and founder of the Centre for UFO Studies — applied rigorous scientific methodology to witness testimony for the first time.

Published the year before the term entered popular culture, this is the source text. Hynek's classification system is still the standard framework used by UFO researchers today.