“Bratva” is one of the latest entries to a flourishing but often unappreciated pocket of the publishing world: tie-in novels. Writers have produced novels based on the terrorism drama “Homeland,” the British crime series “Broadchurch” and J.J. Abrams’s sci-fi series “Fringe,” and more titles are coming soon.

Novels are also providing life support for characters from popular, long-defunct series, like “Veronica Mars,” “Buffy the Vampire Slayer” and “Murder, She Wrote.” (The 43rd and 44th “Murder, She Wrote” novels will come out this year, almost 20 years after the series went off the air.)

Studios and producers have long used novelizations as a way to capture fans’ attention between television seasons, or installments of blockbuster film franchises. For publishers, tie-in books have become cash cows that offer instant brand recognition and access to huge fan bases for vastly larger media. One of the longest running, most successful tie-in series, the “Star Wars” novels, dates to 1976 and now has more than 125 million copies in print.

Writers and publishers of these books usually estimate that 1 or 2 percent of the total audience will buy the book, so a show that draws two million viewers might sell 20,000 paperback copies. “Having that built-in audience, you don’t know that everyone’s going to show up, but you know that a certain fan will show up,” said Michael Homler, an editor at St. Martin’s Press who acquired the “Sons of Anarchy” novel.

Still, in literary circles, these books have often been ignored or sneered at as mere merchandise rather than art. “They’re treated like the lunch box or the action figure,” said Max Allan Collins, who has written dozens of novelizations of shows and films, including “Saving Private Ryan,” “American Gangster” and “CSI.”