The point was that "day people" are persuaded of the value of things by made-up lists, which don't necessarily have any foundation. The repeated requests allegedly put the non-existent book onto the bestseller lists of multiple newspapers, and the hoax was ultimately exposed by The Wall Street Journal. Shepherd and Theodore Sturgeon then wrote the book (under the Ewing name) for Ballantine Books. At another time (between 1956 and 1960), Shepherd called for a "milling" of listeners at a particular date and time in front of Wanamaker's burned-out department store at 4th Ave. and 9th St. in New York City.
I've assembled a small amount of information on Shepherd and flash mobs, with links to other online sites on Shepherd, at http://www.discord.org/~lippard/flashmobs.html.