IT's been billed variously as "mummy porn", "exploitative and sadistic" and an "S&M Cinderella".
It sold its 10 millionth copy earlier this month and got banned from libraries in various US states including Florida, the pacemaker capital of the world (probably quite wise, that.)
Last week, Forbes reported that sales of sex toys have shot through the roof on the back of its success and Universal Pictures snapped up the film rights for $5m. That's when I decided I could ignore the hype no longer.
So I emailed the Herald features editor and volunteered to take one for the team. "I'll do it!" I wrote. "I'll read Fifty Shades of Grey, so you don't have to."
One weekend later, I'm not sure I'll ever recover. Or at least, I'm not convinced my literary sensibilities will.
This is a book for people who like a bit of slap and tickle in the bedroom, but what author EL James - a TV executive and London-based mother of two - has done to the English language is more akin to a flogging to within an inch of its life.
It is Mills & Boon in bondage gear; Pretty Woman with nipple clamps. And, yes, even typing those words makes me wince.
The eponymous hero -- for 'hero', read emotionally bankrupt cretin -- is Christian Grey, a 27-year-old "multi-multimillionaire, billionaire, whatever-aire" chief executive of something who has made lots of money doing important stuff possibly involving helicopters and Sudan. You don't really need to know, because this is not that kind of book.
What you need to remember about Christian is that he doesn't do "vanilla sex", his house has a little "red room of pain", and he has grey eyes.
Christian's eyes take on a life of their own in this book. They crop up with such regularity - "his grey eyes hooded and speculative"; "his cloudy gaze"; "his eyes are alight with some wicked thought"; "his eyes burn into me"; "his grey eyes are alight with curiosity"; "his hot grey gaze is on me", etc - that you imagine they'll want their own credit in the movie version.
Meanwhile, lover Ana bites her lip so frequently, I started imagining her with dirty great scabs all over her face, which slightly spoils the fantasy element.
Of course, Christian's not just a pair of eyes -- he's also a deep thinker: "Why is anyone the way they are? That's kind of hard to answer. Why do some people like cheese and other people hate it? Do you like cheese?" he asks at one point. (That noise you hear? That'll be the sound of Kafka turning over in his grave.)
The breathless narrator is ingénue Anastasia Steele, whom he toe-curlingly refers to as "Miss Steele" throughout. She is a student of literature and a virgin until she meets Grey when she's interviewing him for the college newspaper.
Then he makes her an offer she can't refuse: if she will be his sex slave and allow him to do all manner of things with whips and medieval torture racks he will, er, buy her a MacBook Pro, a car and new clobber. Naturally, Ana jumps at it.
So why have 10 million people bought this book? Well, sex sells. But if that's the only reason they're buying it, there must be a lot of frustrated people out there -- it's page 78 before they even have a snog.
Happily, after that things do hot up fairly quickly. Considering Anastasia has never managed to so much as touch herself "down there", as she puts it, it's impressive that he gives her four orgasms on their first attempt at intercourse. The rest of the book continues in similar fashion.
There are a few whips and chains, but gradually Ana coaxes him into dabbling in, if not vanilla sex, then something closer to caramel.
The Kindle, Amazon's ebook reader, is being credited with much of the success of this book. I suspect that's part of the reason - but much more of it is down to the reason why anything sells in large numbers. And that's clever marketing.
To be honest, I found this book about as erotic as a stale cheese sandwich, but it wasn't entirely without merit. It was by far the funniest thing I've read this year. In fact, I laughed so much I may have turned fifty shades of scarlet.