Mobile phones may be getting bigger, but books could be heading in the other direction if a new format of petite page-turners takes off.
Publisher Penguin Random House is hoping these miniature books, which can fit in a pocket or snugly in one's hand, will revolutionise reading on the go.
It has launched an inaugural set of Penguin Minis featuring four titles by bestselling American young adult novelist John Green, including The Fault In Our Stars (2012), a book about a doomed love affair between two teenage cancer patients which was adapted in 2014 into a hit movie starring Shailene Woodley and Ansel Elgort.
Green, who has more than 50 million copies of his books in print, says in a statement: "When my publisher first approached me with this idea, I didn't even hesitate."
He adds that the Minis "by some magic, contain all the words I've put into my novels in this compact format".
"I'm excited to see which of my favourite books come next," he says.
The other Green titles printed as Minis so far under Penguin imprint, Dutton Books for Young Readers, are unabridged versions of Looking For Alaska (2005), An Abundance Of Katherines (2006) and Paper Towns (2008).
The Minis measure 12cm by 8.2cm. They are printed on ultra-thin paper with a hinged cover that swings open. When closed, they have the surface area of a smartphone and when opened, about the size of a Kindle.
They turn reading on its head as the words run across the pages in landscape format rather than portrait.
The format is based on the dwarsligger ("dwars" in Dutch means "crossways" or "contrary" and "liggen" means "to lie"), a patented design by Dutch printer and publisher Royal Jongbloed first introduced in the Netherlands in 2009.
It has since sold nearly 10 million copies in nine countries with works by authors ranging from Dan Brown to F. Scott Fitzgerald.
Ms Julie Strauss-Gabel, president and publisher of Dutton Children's Books, says over e-mail that when she saw the Dutch dwarsliggers of Looking For Alaska and The Fault In Our Stars, she was instantly taken by the format, which she called "clever, practical and absolutely charming".
"We've all become accustomed to mobility, but we know many, even most, readers still prefer print," she says.
"The dwarsligger is the perfect solution for book lovers who still want the flexibility of e-reading. It's great for travellers and commuters, or anyone who never wants to be caught without a book."
The John Green Minis have an inaugural print run of 500,000 copies. Penguin Young Readers has slated additional titles for next year.
The new format has yet to catch on in Singapore, where the Minis are available in Books Kinokuniya and selected Times bookstores.
Beijing Institute of Technology Zhuhai assistant professor Aaron Ho, the man behind Instagram account @mrtreads, which documents people reading on the MRT through netizens' contributions, says, however, that size does not matter that much to Singapore readers.
The 38-year-old says hefty tomes such as J.K. Rowling's Harry Potter books and some of Haruki Mura-kami's novels have been among the most popular on @mrtreads for the past two years.
"People don't mind carrying around big books if the books interest them," he adds.
What is important, he adds, are features such as font size, paper thickness, tactility and, of course, the readability of the book. "Singaporeans are curious about new things and the books may sell well."
One drawback customers have noted is the price of the books. At Kinokuniya, a normal paperback copy of The Fault In Our Stars costs $17.66, while the Mini version is $20.87.
Singaporeans associate size with value for money, says human resources manager Jason Fok, 44. "That something so small would cost more is going to put people off."
Still, others think the Minis show promise.
Hougang Secondary School student and avid young adult fiction reader Phoebe Teo, 13, says: "I usually have a lot of books to carry, so Minis would be a convenient size to take along."
Medical social worker Hafiz Wahid, 34, a horror and mystery book fan, says: "They are easier to flip. If they put out Stephen King in this format, I would get it."
•The Penguin Mini versions of Looking For Alaska, An Abundance Of Katherines, Paper Towns and The Fault In Our Stars are available at Books Kinokuniya and selected Times bookstores at $20.87 each or $82.34 as a four-volume set.