Fascination With “Mommy Porn” Waning?

I was somewhat relieved to read that, for the first time since publication, sales of Fifty Shades of Grey are in decline. This comes from the BBC:
Sales of E L James’ Fifty Shades trilogy of erotic novels have fallen for the first time in two months.

After increasing for eight consecutive weeks, last week sales slipped by 16% to 1.21m (£5.4m), according to industry publication The Bookseller.