The double standard has been around for a long time, actually. Most "Romance Novels" have some level of sexually explicit content in them, with a fairly large branch of them being hardcore porn written for women. Any major bookstore chain or library will have a gigantic section dedicated to these novels and middle aged women buy them up like crazy. If you're not familiar with what they look like, if you find yourself surrounded by pink books with half naked ridiculously muscled guys on the covers, you've found them.[footnote]Ironically, this has become a reason that women have cited for buying e-book readers. They can read the novels in public without people raising eyebrows at the contemptible covers that are inevitably associated with the genre.[/footnote] Meanwhile the occasional mainstream bookstore might have a shelf tucked away in back dedicated to "Erotica" and most of that is probably still geared to women, but it is somehow regarded as much less acceptable than the exact same kind of content that is packaged as a romance novel.
It is very unusual for one of these books to get this much exposure though. It's a weird confluence of the popularity of Twilight, the "out-of-effing-nowhere" status of the author, the fabricated controversy over the sex scenes, and some honest to goodness staring at a train wreck onlooking.
As for the quality, after seeing some of the hilarious dramatic readings on youtube[footnote]The one done in the style of Cookie Monster was especially funny[/footnote] I decided to try reading it myself. I didn't last until the first sex scene. The characters make the Twilight protagonists look like deep and well rounded characters. They're cardboard cutouts that were then flattened with a steamroller. The protagonist keeps constantly switches from weirdly hilarious curse filled dialogue to referencing classic literature for little to no reason. You can almost hear the author saying "See! I'm well read! See that right there! That proves I'm smart!" The awkward writing, the annoyingly shallow characters, and the incredible creepiness of the relationship before they even get to the torture sex was enough to convince me that whatever hilarity was buried in there wasn't worth the slog through the rest of the book.