The novel "Fifty Shades of Grey" by E.L. James has been propelled by its e-book sales to bestseller status. Published by a small Australian press, it has had a hard time making its way to bookstores, but readers are getting it however they can. Mostly, that's been digitally.

"Fifty Shades of Grey" is about a 22-year-old college literature student, Anastasia, a virgin who falls for a 28-year-old entrepreneur, Christian Grey, who gets a sexual charge out of being in charge. It's explicitly tie-me-up, tie-me-down; sometimes a necktie is not just for tying around necks.

The New York Times calls the book "mommy porn." Jezebel, which posts some not-safe-for-work excerpts, explains that "Fifty Shades of Grey" owes a great debt to the bestselling "Twilight" series.

British author E.L. James, a former television executive, first published the book on fan fiction site ff.net as a super lengthy tome (the first book is 1200 pages, but the original also included the following two sequels) that "reimagined the Bella and Edward love affair set in contemporary Seattle, Washington with Bella as the young college graduate virgin and Edward as the masterful billionaire with secret sexual predilections." If that description makes you want to gag, you probably won't be into James' book, either — but if you're a diehard member of Team Edward who's sick of Stephanie Meyer's G-rated prose, you'll be all over the story of literature student Anastasia Steele, who first meets the successful young entrepreneur Christian Grey when she interviews him for her campus magazine.

"So many readers have recommended this book to me," wrote Sarah Wendell at her well-known romance book website (adult language). "SO MANY." Wendell, an enthusiastic romance reader, didn't think much of "Fifty Shades of Grey" when she read it in November. "I found it to be melancholy and meandering, and the heroine narrator is so maudlin and wimpy I grew more and more irritated with her and with the story and had to stop," she wrote. She maintains her critical take, but adds this commentary on the book's popularity:

I have a few theories as to why this book is popular. It has a secrecy element, for example, similar to some paranormal romances and their avid fanbases. It's also not at all surprising that 50 Shades and Twilight share a few plot themes, specifically that secrecy and the temptation inherent in the world of both narratives, and the alpha male who is opulently, ridiculously wealthy, Volvos optional. Plus, Edward, as I wrote a few years ago, and in many similar ways (again, surprise surprise) Christian are both very much old-skool-style romance heroes. 50 Shades (and Twilight, obviously) are also told from the heroine's POV, a very deep, first person, detail-heavy point of view, and the narrative is also akin to reading a diary, adding to that sense of illicit secrecy .... In Twilight, the secret world and the key to entry is the knowledge that Edward is a vampire, knowledge only Bella, and by extension the readers, initially share. In 50 Shades, the secret world focuses on sex, specifically Christian's secret room and his sexual expression through BDSM. Sex, in many senses, is the initial conflict of 50 Shades book, and is the obstacle between the characters initially as well, and thus becomes a focus. So the secrecy is layered and complex.

The secrecy of e-books may also have fed into the book's popularity. Nobody knows that you're reading a titillating BDSM book when it's on the screen of your Kindle; you could just as easily be reading about organizing closets. But when the cover is on display, everyone knows what you're up to.

Publisher Vintage Books is willing to risk the risque; last week it purchased American rights to "Fifty Shades of Grey" and its two sequels, "Fifty Shades Darker" and "Fifty Shades Freed." Vintage's e-books are coming soon; paperbacks are expected to arrive in bookstores in April.

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-- Carolyn Kellogg