Fifty Shades of Grey is just Jane Eyre rehashed - young virgin falls in love with rich powerful man. Same story, just a little bit more descriptive when it comes to the sex scenes.
The similarity ends on the plot summary level -- which is the most superficial part in literature.
It's also 20 levels below in writing quality, like a messed up straight 20,000 lines amateur PHP monstrosity compared to something written by Rich Hickey.
