IN HIS international bestseller “ The Hare With Amber Eyes ”, Edmund de Waal traces the fortune of a collection of carved Japanese netsuke figurines. Readers grew so entranced by the story of these objects that they started clamouring to see them. So after the hardback, the e-book, and the paperback came the deluxe illustrated edition last November—along with something called the “enhanced” digital edition The illustrated hardback “Hare” is an object of impeccable book design, elegant without feeling chilly. The enhanced digital edition includes the same family photographs, memorabilia and maps, plus embedded videos of Mr de Waal touring readers through the story in Paris and Vienna. Mr de Waal, a potter with a rich concern for the tactile qualities of objects, hopes that the illustrated edition feels “like a book that you want to pick up, an object to be held.” Yet his multimedia e-book involves holding a smooth, flat iPad, Nook or Kobo. And it is behind the hard screen of such devices that ever more of our books will soon be found.Inspired by the commercial success of mobile tablets, publishers are now experimenting with the medium in earnest. Sales of multimedia-friendly tablets, smartphones and e-readers are set to grow in America to 1.1 billion by 2015, up from 450m today. And Apple's iBookstore gives publishers a welcome place to sell their wares that isn't Amazon.Print purists needn't retreat with horror to their laden shelves. Multimedia enhancement will still affect only a tiny proportion of new titles. Children's books were first to get this bells-and-whistles treatment, but adult fiction has proven a harder sell. Few readers have been willing to pay more for extras at the back. While ordinary e-books continue to eat into print sales, a British experiment with adding author videos and other material to best-selling novels, called Enhanced Editions, was quietly abandoned last year.Yet for certain kinds of book, such as biographies, cookbooks, literary classics and newer forms of interactive fiction, enhancement can add rich and startling new layers. Penguin's forthcoming biography of Malcolm X, for instance, features rare archival footage and an interactive map of Harlem. The life of “ Muhammad Ali ” now comes with audio clips of him rapping about his prowess. Richard Dawkins's “ The Magic of Reality ” (voted best app at the 2012 Digital Book World) and E.O. Wilson's “ Life on Earth ”, are cunning fusions of documentary and textbook, with molecules and stories spinning at a finger's touch.Timeless classics have also proved to be good candidates for a bit of extra gloss. Breaking a losing streak of enhanced apps that failed to turn a profit, a multimedia edition of T.S. Eliot 's “ The Waste Land ” swiftly earned back its cost for Faber & Faber, says Henry Volans, the publisher's digital director. The “book” serves up Eliot's original manuscript with footnotes and scholarly addenda, as well as video and audio recordings of the poem in performance. And this spring Faber will reach for the brightest star in the literary firmament and publish Shakespeare's sonnets. Penguin, meanwhile, chose as its inaugural “amplified edition” the modern classic “ On the Road ”, featuring archival photos of Jack Kerouac's original manuscript typed on a scroll, along with snapshots of his fellow Beats, some video interviews and maps of the cross-country journey.Experiments in what Mr Volans calls “the fiction challenge” are popping up all over. The enhanced edition of George R.R. Martin's fantasy epic “ Game of Thrones ” links the names of characters to a glossary of clans and furnishes a one-touch map; Ken Follett's “ Fall of Giants ” includes a custom soundscape. (Sound is far less “prescriptive” than an image, so it leaves more room for reader imagination.) Pop-up biographies in the margins of "On the Road", however—purportedly of those who inspired Kerouac's characters—feel jarring.The labels attached to these hybrids reveal the tension at their heart. They're not exactly books, but “amplified,” “enriched”—even “interactive narrative” experiences, as in the case of the children's tale “ The Fantastic Flying Books of Mr Morris Lessmore ”. With literature, especially, many readers remain rightly sceptical of narrative intrusions that disrupt the creation of what Robert Olen Butler, an American novelist, calls “the cinema of the mind.”Mindful of this delicate balance, publishers are nonetheless eager to test the creative and commercial possibilities of such enhancements. “As e-books merge and become as interactive as apps, you have just an incredible new opportunity,” says Rachel Chou, chief marketing officer at Open Road Media, a digital publisher in New York. The company's new “e-riginal” " Listen to Bob Marley ", includes a function allowing readers to tweet a quote directly from the book. Dan Franklin, digital publisher at Random House UK, agrees that the best projects will be born digital, an organic fusing of form and content. “It's all about inventing things the reader doesn't know yet that they'll love.”The first examples of new digital storytelling forms are now arriving. It's no accident that they're aimed at young adults. Penguin's new release, " Chopsticks ", a young-adult love story, uses digital scrapbooking and bits of text interspersed with music tracks and YouTube clips. Open Road's " Gift ", due out in March, is a ghost story told with audio tracks and music videos, as well as a graphic novel with sound and visual effects. Perhaps the most successful blend of old and new, though, managed to elicit audible gasps at a Futurebook conference in London not long ago: it is a small-press book of digital pop-ups in which the letters of poems start to dance.