From contemporary accounts, both written and personal, it had a huge impact when it was published. It was widely read. You can see that in some of the quotes above “I thought surely I’d read it.” Because most women of the era had read it, even if they had to sneak copies to each other. When Fifty Shades of Grey was everywhere, I imagined it was a bit like that. Excerpts floating around. Some flaunting reading it, some hiding reading it. Everyone discussing it.
Some time in there, it switched from everyone read it, to everyone assumed they had read it and that they knew what it said.