In the note above the copyright of the book it states:
The text owes much to Marshall McLuhan who, in fact, co-authored an earlier version. We are indebted to the authors quoted and their publishers, and to Harper's Bazaar in which some portions of the material appeared.The obituary for Edmund Carpenter in The New York Times on July 7, 2011, included this paragraph:
His collaborations with McLuhan included numerous jointly written articles and the anthology “Explorations in Communication” (1960). The article “Fashion Is Language,” which appeared under McLuhan’s name in a special McLuhan issue of Harper’s Bazaar in 1968, was actually written by Mr. Carpenter after McLuhan went into the hospital for brain surgery. It was published in book form, in 1970, under Mr. Carpenter’s name, with the title “They Became What They Beheld.”
There is a footnote in McLuhan is Space: A Cultural Geography (2003) by Richard Cavell which states:
Edmund Carpenter suggest that he was the author of the Haper's article, though when it appeared in an altered version as part of Carpenter's They Became What They Beheld (1970), Carpenter credits McLuhan's input into the volume. See Carpenter's Remembering Explorations,' Canadian Notes and Queries 46 (Spring 1992): 3-15; reprinted in a slightly different form in Theall's Virtual Marshall McLuhan.So I went to "The Not-So-Silent Sea," Appendix B of Virtual Marshall McLuhan where Edmund Carpenter wrote:
Harper's Bazaar commissioned Marshall to write a special McLuhan issue. He was about to undergo surgery. The fee was large & needed. Not a word had been written, not a photograph assembled. On Friday, the publisher warned me: if an acceptable manuscript wan't in his hands by 9 a.m. Monday, the contract was cancelled. It arrived on time and appeared under Marshall's name. Three years later it appeared as a book, They Became What They Beheld, under my name.Out of curiosity I will probably buy the April 1968 issue of Harper's Bazaar from ebay. But given the above information, it is pretty clear to me that Edmund Carpenter deserves the credit for both works.
I think of these two works and Understanding Media as collaborative efforts of two brilliant men and very close friends. In the former, Carpenter completed the work, in the later, McLuhan completed the work. Collaboration is difficult in print and authorship is not always an easy definition.
In my opinion, They Became What They Beheld deserves the same respect as any McLuhan book. Highly recommended.