Great vs. Gatsby

On April 11, 1925, The Great Gatsby by F. Scott Fitzgerald hit the shelves. On April 8, 2014, Great by Sara Benincasa hit the shelves. It's supposed to be a retelling.
From the publisher:
In Sara Benincasa's contemporary retelling of The Great Gatsby, a teenage girl becomes entangled in the drama of a Hamptons social circle, only to be implicated in a tragedy that shakes the summer community.
My first reaction when I saw the ad for this book was surprise. I've read retellings of Peter Pan and Pride and Prejudice. But Gatsby? Can they do that?
For those of you who haven't read The Great Gatsby and would like to know what's going on, I'll sum it up. For those of you who intend to read The Great Gatsby in the near future, skip this paragraph, you'll understand enough. Spoilers ahoy.
Nick, our narrator and audience surrogate, tells the story of Daisy and Tom Buchanan. The Buchanans are a rich and miserable couple. Tom's cheating on Daisy with a poor and miserable mechanic's wife. Daisy either doesn't know or doesn't care. Then Jay Gatsby, her old boyfriend, shows up. They innocently hang out a few times and Tom, hypocrite that he is, reacts as if she's having an affair. Daisy and Gatsby are out joyriding one day when Daisy runs over the mechanic's wife. Oopsie. The mechanic tracks down the car and shoots Gatsby in revenge. The Buchanans move and Nick breaks up with his girlfriend, Jordan. The End!
END SPOILERS.
Benincasa's Great changes all of the names and some of the genders. Jay Gatsby is now Jacinta, Daisy is Delilah, Tom is Teddy, Nick is Naomi, and Jordan, the girl Nick dates in The Great Gatsby, has now transformed into Jeff. Couldn't he be Jordan? That's unisex.
I've been thinking a lot about retellings lately. See my post on updating Annie here. I'm not sure how well this story can transition into a modern setting. The Great Gatsby is so firmly set in the Jazz Age that my history textbook cites it when defining the time period. Type the name of F. Scott Fitzgerald's wife, Zelda, into google and the first thing to come up is "Zelda Fitzgerald flapper". The wikipedia page for flappers uses Daisy Buchanan as an example. The plot also revolves around Prohibition, since Jay Gatsby is a bootlegger.
There are no flappers and bootleggers today. Wild girls? Yes. Drug dealers? Yeah. Crazy parties, like the ones in Fitzgerald's book? Yep. But it's not quite the same.
Jacinta is not a bootlegger. She's a fashion blogger, which means modern technology plays a role in the story. Another change is sexuality. Since the Daisy character isn't genderflipped like many others, he's now a lesbian. That changes the whole relationship dynamic.
Then there's the characters' ages. I am a teenage girl. I love book about teenage girls. As I read The Great Gatasby for English class, one thing that disappointed me was the lack of teenagers. But I understood it wasn't that kind of book. The core of the story is the Buchanans' affairs. A high school aged couple cheating on each other is not the same as a married man and father taking on a mistress. The story didn't work with teenagers. Can this one-while still staying true to the story?
So, Benincasa changed the characters, setting, and plot. What storytelling elements does that leave? Dialogue, maybe? Theme? I'm curious to see how this turns out. I'm pretty sure I can guess at the tragedy at the end of the book because I've read the original.
As Great has just been recently released, most of the reviews I've seen are from adult book bloggers. They have vague memories of reading Gatsby in high school and compare Great to the new Leonardo DiCaprio movie instead. I want to know how it stacks up to the actual book. Can it really be called a retelling, or is it a completely new story with a few allusions to Fitzgerald's novel?
I won't pass judgment on a book I've never read. For all I know it really is great. But retelling Gatsby makes me worry for other twentieth century classics. Exactly how long will it be before we see To Kill A Mockingbird reissued as Kill or The Catcher in the Rye reduced to Catcher? I can see it now. Let's name Holden Caulfield "Holly" this time around.
What do you think? How faithful does a book need  to be to the original before it can qualify as a retelling?