[5] The book features the first publication known of the concept of a "man in black",[3] later expanded into UFO folklore by Gray Barker in his 1956 work They Knew Too Much About Flying Saucers.

Chapter Seven, "Comments on the 'Project Saucer' Report" features conspiratorial speculation about military secrets and a chemical analysis of the slag rocks from Tacoma.

"[7] Air Force UFO investigator Edward J. Ruppelt doubted the book's accuracy, noting: "As Arnold's story of what he saw that day has been handed down by the bards of saucerism, the true facts have been warped, twisted, and changed.

Even some points in Arnold's own account of his sighting as published in his book, The Coming of the Saucers, do not jibe with what the official files say he told the Air Force in 1947.

[10] Popular science writer Martin Gardner argued that "no one can deny that [Palmer] played an enormous role ... in tirelessly promoting the craze".