For fans of TV Land's "Younger," the June 5 season premiere was a must-watch. The TV show takes place largely at the offices of Empirical Press, the fictional publishing house where main characters Liza (Sutton Foster) and Kelsey (Hilary Duff) work, and the new season found the women gathered around a pile of glossy, green books.
It was a shipment of the book "Marriage Vacation," the writing of which was a central plot line in season four. On the show, it was written by character Pauline Turner Brooks (Jennifer Westfeldt).
On the same Tuesday, "Marriage Vacation" launched in real life, published by Simon & Schuster.
It's a case of life imitating art, and this type of immersive experience could soon be the new norm.
"I think things along these lines are the future for books," Jo Piazza, the ghostwriter of "Marriage Vacation," and author of five books (a sixth is slated to publish this summer), tells CNBC Make It. Though character Brooks is listed as the author on the IRL "Marriage Vacation," it's Piazza's handiwork.
Given that publishers' book sales for trade (consumer) books were flat in 2016, according to the Association of American Publishers, and the Adult Books category saw a 2.3 percent decline, riffing off a popular TV show like "Younger" could be one solution to drumming up excitement around novels.
"The fact that you're competing for eyeballs on all other kinds of content, this is how you can make a book that really stands out, that you can get readers to know that it's out there, and to get them excited about it. So I think finding these kinds of tie-ins is very important to the book industry at this point," says Piazza.
Books that are pegged to popular TV shows also have the potential to create new readership as well.
"These fans might not have read a book otherwise, or they might not be big readers, but they're going to come to this book ["Marriage Vacation"] so it's a win-win for both of us," Simon & Schuster's Christine Pride, editor of "Marriage Vacation," tells CNBC Make It.
"In this competitive media landscape, those are the kind of edges that you're trying to leverage."
Simon & Schuster did not yet have sales numbers, but reader feedback suggests fans are responding: "As a big fan of 'Younger,' I was excited to hear that this book was becoming a reality," writes one Amazon user of the book. "I love the idea of having an opportunity to engage in the plot line of one of my favorite shows in an new, unconventional way. I hope this is the first in a long line of fictional novels from 'Younger' coming to life."
Turning an imaginary book into a real one is not a novel idea — in the early 2000s J.K. Rowling published "Quidditch Through the Ages" and "The Tales of Beedle the Bard," both books plucked from Harry Potter plot lines, for example — but the trend is taking root, and the work is getting better, says Piazza.
Though Adams Media (an imprint of Simon & Schuster) published a real version of the fictional novel "Snow Falling," — written by Gina Rodriguez's character, Jane Gloriana Villanueva, on the CW's "Jane the Virgin" — to mixed reviews in November (it was called "fun," if not necessarily a convincing story line), Pride points to the "Castle" book series' success. Some of the books in this line-up of mystery crime novels written by the fictional character Richard Castle, the star of ABC's "Castle," have landed on best-seller lists.
And now, Pride and Piazza say "Marriage Vacation" takes so-called "fan-lit" to a different level too.
"It was really important to Christine and I to create a real book," says Piazza, who points out she makes her living as a novelist (with titles like "The Knockoff" and "Charlotte Walsh Likes to Win") not as a ghost writer.
"For too long, we have seen so-called chick-lit, rom-coms, women's commercial fiction with women characters who are in their 20s or early 30s where things just happen to them, and it's glitzy and it's glammy," Piazza says. "And 'Marriage Vacation' — while it's fun and frothy — it's also a book about a 40-year-old woman with real emotions and real problems and real issues."
The Washington Post review makes a similar point: "[F]or all its games within games, 'Marriage Vacation' makes a delightful read for die-hard fans of 'Younger' as well as anyone looking to reaffirm that women are capable of whatever they put their minds to — on TV or in real life."
On Amazon, the book boasts a five star rating, with one reviewer saying the book "will resonate with a lot of women."
But of course, the book was carefully written to please fans.
On the show, author Brooks loosely based "Marriage Vacation" on her former marriage to Charles (Peter Hermann), Liza's boss and potential love interest. Piazza had to start there, so late last year, she binge-watched every season in about 48 hours in order to mine the plot lines for content. She also had some of the season five dialogue and plot points at her fingertips to make sure everything lined up.
Series' creator Darren Star (also the mastermind behind shows such as "Sex and the City" and "90210") had input. And Piazza and Pride also received direction on certain things, like making sure the book character Karl, based on the TV show character Charles, is likeable, since Charles is a fan favorite.
And then there are the gems: "If you are a fan of 'Younger,' then all of the hidden, 'Younger' Easter eggs are in there for you to enjoy," says Piazza.
Those "Easter eggs," weaved throughout the story, include the 58th page of the book. During season four of "Younger," the main characters teased that page of Pauline's book as steamy and scandalous. Now, fans can flip right to the NSFW page, and see for themselves what Liza and Kelsey were talking about.
There are also clues from the acknowledgements section of the tome as to how relationships, like that between exes Charles and Pauline, might play out on season five.
"I think the most fun part of this story for fans is we get Charles' backstory," Piazza says. "We get to unbutton his three-piece suit, if you will, and find out what he's like when he's a younger man and in the bedroom and things like that."
For its part, the show "Younger" has been a surprise success since its 2015 debut; it boasts an impressive 97 percent on Rotten Tomatoes and has received critical acclaim. "Younger" also set ratings records for TV Land.
The series follows the life of Liza, a 40-year-old divorcee who struggles to dive back into the publishing world after taking a long hiatus to raise her daughter. To land an assistant job at Empirical Publishing, Liza says she's 26. There she meets Kelsey, a "fellow" millennial.
The hilarity of a 40-something navigating the world as a fresh-faced New Yorker — and the satirical look at the intense, New York publishing world — has resonated with audiences both young and old. The 2016 season two finale drew a reported average of 1.30 million viewers, including 676,000 adults ages 18 to 49.
Don't miss: No selfies, social media or dark manis: The royal 'rules' Meghan Markle is supposed to follow
Like this story? Like CNBC Make It on Facebook!