St. Martin's Press has published five serial novels in the past year, ranging from historical fiction to erotic romance, and has three more in the works. Penguin's digital romance imprint, InterMix, is testing serialized romance and erotica, and has released three titles so far, with several others on the way.
The science-fiction and fantasy publisher Tor recently published a science-fiction epic by John Scalzi in 13 weekly episodes.
Amazon, which is leading the way with the format, has released 30 serialized novels through its new Kindle Serials program and is adding a new series every week. Readers pay $1.99 for an entire series, and new installments update automatically. Like a TV show, the episodes are designed to be devoured in a single sitting and end with a cliffhanger.
"The Charles Dickens model actually fits better now than ever because people want bite-sized content," says writer Sean Platt, who has co-authored six digital serial novels.
The serial model could be a boon for publishers and booksellers. Breaking up a longer work enables them to charge readers slightly more for it. Authors and publishers can also use a gradual digital release to test new series and characters in a relatively low-risk way, and build buzz for upcoming print titles. But digital serials could also be bad for business if they eat away at future print profits—still the biggest revenue source for most publishers.
Publishers and writers are now wrestling with the format, trying to figure out the best price, length, and intervals between installments.
Jeff Belle, vice president of Amazon Publishing, AMZN +0.35% says the company is still trying to "fine-tune" its serial-publishing program based on reader responses. Amazon launched its serials last fall with 10 novels. The company has since added 20 more series, which range from romance to crime to supernatural thrillers. The best-selling title so far, Andrew Peterson's thriller "Option to Kill," has sold some 80,000 copies.
"Early data indicate that shorter is probably better, and a one-week cadence works best," Mr. Belle said.
Others worry that if readers are forced to wait, they might not return. In an era when people binge on streaming TV shows and can instantly download all 20 books in their favorite crime series, the weekly-appointment model might not hold up, says Dan Weiss, publisher at large at St. Martin's, who has overseen the development of several serials.
"We originally thought it would be fun to publish brief books with cliffhangers, and publish them like a TV show on a weekly schedule," Mr. Weiss said. "But since then, with 'House of Cards,' binge viewing has come into vogue," referring to the original TV series that Netflix released all at once. St. Martin's may try publishing several episodes at once, he said, because their brevity makes them "easily digestible and phone-friendly."
Romance novelist Beth Kery wasn't prepared for the vicious backlash to her novel, "Because You Are Mine," which InterMix published last summer in eight weekly installments. The book was a hit, selling more than 500,000 copies. But some of Ms. Kery's longtime fans detested the format. Some readers were outraged over the $1.99 price tag for each installment, which added up to $16, far more than many e-books cost. Others resented being teased with cliffhangers.
"I am really sick of sitting down to read this book and just when you are enjoying it, it ends," one Amazon reviewer seethed. "Release the whole book, I would enjoy it more," another wrote.
This month, Ms. Kery's publisher finally released the complete story as a $16 paperback. It's also available now as a single digital volume, for $9.99. Ms. Kery is currently releasing another eight-part serial romance, "When I'm With You."
Publishing a novel in increments poses additional challenges for writers, who have to worry about readers dropping off mid-series, as well as new readers coming to the novel in the middle or toward the end.
Mr. Scalzi, a best-selling science-fiction novelist who released his new book serially with the imprint Tor, says he struggled at first with the unfamiliar format.
He wanted to make sure the 13 individual episodes could stand alone but also added up to a single, seamless story for readers who chose to wait and consume it in a single serving. (Tor will release a print edition of "The Human Division" next month.)
The novel has been landing on Amazon's science-fiction best-seller list every week, and sales have grown with each episode. When the final episode came out this week, Mr. Scalzi announced that the saga would continue, telling fans on his website that the serial "has been renewed for a second season."