"Anatomy of a Phenomenon: Unidentified Objects in Space - a Scientific Appraisal" published in 1965 was Jacques Vallee's first book on the UFO phenomenon in the English language ("Challenge to Science" had been published only in French and the English language edition came later). The book sold well through the mid-1960s, against the expectations of the American publisher Neville Spearman.
The UFO issue had entered popular mythology and up to this point been variously sensationalised or ridiculed in the mainstream media. Vallee's book attempted to introduce a more scientific approach to the public for the first time. The early chapters present detailed evidence of the reality of UFO-type phenomena throughout history and into modern times. Meticulous documentation of sightings and encounters from across the world and an evaluation of the probabilities of extraterrestrial life (in the second chapter) led him to petition scientists to recognise that a real phenomenon existed and should be studied.
Vallee noted that, to his view, many encounters did not seem to fit the model that they might be extraterrestrial visitors but might be some other (still real) phenomenon. He argued that the subject was important and should be studied to discover the truth of what they actually might be. In the later chapters, he tackles the overly emotional and unscientific reaction he perceived from most scientists when confronted with the evidence - what he terms "The syndrome of resistance to the future." The process of normal interpretation employed by science in investigation is, Vallee observes, "to distort a set of unknown phenomena until it is recognisable by ordinary standards:" UFOs cannot be of intelligent non-human origin because this hypothesis doesn't fit in the current box of what is possible and what not possible, so the way to deal with the evidence psychologically is to either ignore it completely, or else distort it until it fits and can be explained away using current dogmas. This he identifies as the core issue: evidence of the extraordinary is plentiful and compelling, but dogma and emotionalism, rather than science, buries the issue because of its challenge to current paradigms.
Vallee attempts to categorise phases of UFO behaviour into three distinct groups according to interaction, duration and type - similar (but not concurrent or identical) to Allen Hynek's classification of encounters of the first, second and third kinds. He always seeks patterns: waves of reported sightings in specific locations, for example.
The final chapters are devoted to an examination of (some mainstream and a few original) hypotheses about what the whole UFO/humanoid alien contact phenomenon might be. The ideas of Misraki (who studied mythological and ancient cultural references to sky gods as possibly describing extraterrestrial interactions), Duncan Fletcher and the French Ufologist Aime Michel are all examined and evaluated.
Vallee's conclusion, in a nutshell? We have a real phenomenon, not a fantasy, and it needs to be investigated with science. Do we know what it is? No. Might extraterrestrials be the agency behind the phenomenon? They might, but this is unproven: some other paranormal/metaphysical agency might be behind the phenomenon. But until we agree as an academic community to look into it, we're unlikely to find out, as it does not overtly reveal itself to us.
Like Vallee's later books on this issue, "Anatomy of a Phenomenon" is original, thought-provoking and worth reading - though in his attempt to remain detached and scientific, the author can at times be a bit too cerebral - and don't expect easy answers or conclusions.
If you can find a good original hardcover edition from the 1960s complete with all the photos, graphs, charts and maps, then buy it - it'll be a good investment, and a good read.