A good book is a good book

I have been mostly ignoring the phenomenon of the awful "Fifty Shades of Grey" books after reading an early (dismissive) crit. of the first book but have been dismayed to see these books escalating up the 'best seller' lists. So, today I was very pleased to read a newspaper report, where a writer described the books as "a bad literary joke" and "a triumph of marketing over substance". This writer also stated that "millions have bought these books" and that "millions have wished they had kept their money in their pockets". I agree with all this, but what made so many people buy this trash? Was it really marketing? Or was it mere stupidity and people being unable to think for themselves? A combination of the two, I imagine.
Meanwhile I will return to my biography reading and then branch out into some decent fiction.