I wouldn't waste my time even picking up a copy of 50 Shades of Grey, which is a mass market piece of tripe for bored women.
On the other hand, the Story of O is a classic piece of erotica published in the 1950s, the authorship of which remains something of a mystery. Pauline Reage is the pen name of Dominique Aury, itself the pen name of Anne Declos, a French author and journalist. She wrote The Story of O as challenge after her lover claimed that a woman could not write and erotic novel.
There is not a lot of plot - it is a series of degrading sexual experiences involving bondage, whippings and brandings, a total subservience to the men in O's life.
However, the constrained language certainly ensures that this is genuinely erotic and not just titillating.
She wore her sexuality with an older woman's ease, and not...like an awkward purse, never knowing how to hold it, where to hang it or when to just put it down.
White Teeth, Zadie Smith