We're barely halfway through the year, but it seems a safe bet that the so-called "mummy porn" novel Fifty Shades of Grey will be the fiction sensation of 2012.
It's the fastest selling paperback since they started keeping records, and the first E-book to sell a million copies.
Author Erika Leonard, a middle-aged Englishwoman who writes under the pseudonym E.L. James, is reportedly raking in $1.7 million a week in royalties.
I haven't read the book and can't imagine any circumstances short of it being washed up on the desert island where I'd been marooned for several years with nothing to read that would persuade me to do so, but the emerging consensus among those who have is that it's simultaneously (and paradoxically) excruciating and laughable. It's often referred to as Fifty Shades of Brown.
For those who have no desire to wallow in this sea of dross but wouldn't mind dipping their toe in it out of curiosity, American blogger Cassandra Parkin has performed a heroic public service by assembling illuminating snippets under the heading "Fifty things that annoy me about Fifty Shades of Grey."
My favourite was this rumination from our heroine, shy, virginal Anastasia Steele, after her first meeting with the handsome, mysterious tycoon who will be her guide on her voyage of self-discovery which seems to begin and end in his Spanish Inquisition style "playroom": "No man has ever affected me the way Christian Grey has and I couldn't fathom why. Is it his looks? His civility? Wealth? Power?"
Anything's possible I guess, but what about his Kim Dotcom impersonation?
Women are always saying they like a man who can make them laugh.
When something like this comes along, there's never a shortage of people trying to work out what it means. What is its cultural significance? What does it tell us about contemporary society?
More often than not, they overlook the obvious and attribute unwarranted significance.
For a start erotica written by women isn't as uncommon as some of those attempting to interpret the phenomenon seem to think. Before Fifty Shades came The Sexual Life of Catherine M (2001), The Bride Stripped Bare (2003), 100 Strokes of the Brush Before Bed (2004) and Wetlands (2008), all of which were deemed "shocking" thereby guaranteeing their commercial success.
Before them there were films like 9 Weeks and Wild Orchid which, in addition to setting Mickey Rourke's career back 20 years, had virtually the same storyline as Fifty Shades: innocent young woman meets worldly, mega-rich older man, submits to his will, achieves self-knowledge and liberation through immersion in kinky sex.
Take out the kinkiness and that's pretty much the premise on which countless Mills & Boon books are based.
Writer Estela Welldon told the Guardian that "it's a terrible turning back of the clock for a book like this to have such enormous success. It's as if women are now trying to apologise for the success they've had in a man's world".
That seems a stretch. You could argue all day about why women want to read this stuff, but I suspect a large part of the answer is: because they can.
In the Kindle age you can buy these books without having to face another human being, which takes public embarrassment out of the equation; and if you're so inclined, you can read them on the bus without having mothers hustle their children as far away from you as possible.
The issue exercising some readers and almost all critics is: how can a book this bad be so successful? Perhaps the answer's staring them in the face. Re-frame the question as a proposition, and all is revealed: the book is this successful because it's so bad.
When it comes to titillation, it may well be that any attempt to package or enhance the raw content just gets in the way. After all, pornography generates huge revenues by operating on the principle of "never mind the quality, feel the width".
We don't know why one book or film or album achieves commercial success while others disappear without trace.
As legendary screenwriter William Goldman wrote in his Hollywood memoir Adventures in the Screen Trade: "Nobody knows anything. Not one person in the entire motion picture field knows for a certainty what's going to work."
But what we do know is that when something is, for reasons no one can quite explain, the right product at the right time, the fact that it's unadulterated crap won't stop it being a hit.
Maybe Fifty Shades is this year's The Da Vinci Code.
Dan Brown's widely derided yarn was 2003's publishing sensation, yet this week English charity Oxfam reported that Brown has topped its "most donated" author list for the fourth consecutive year.