Best-selling authors Neal Stephenson and Greg Bear have launched The Mongoliad, the first digital novel on a so-called social book platform that will allow them to add new elements such as music, video and reader-generated content to the book.

The two authors released the first chapter, along with artwork, a map and other materials of The Mongoliad on Wednesday. Stephenson and Bear will release new chapters of the speculative fiction novel, set against the Mongol invasion of Europe in the 13th century, in weekly installments, according to a press release. New chapters will be available on the Web and on handheld devices, starting with Apple's iPad, iPhone, and iPod Touch.

The authors will collaborate with readers through Pulp, a participatory publishing tool from Subutai, a publishing technology company with Stephenson as its chairman. Five other authors, as well as artists, fight choreographers and other experts, will contribute to the book.

"Pulp is what Gutenberg would have come up with if he hadn't jumped the gun and released 600 years early," Stephenson said in a statement. "Kindles and iPads were little better than expensive drink trays until we came up with this."

Readers will be able to add to the 'Pedia, the online encyclopedia that describes the Foreworld, the world where the book is set.

"The form of the traditional novel is a consequence of the technology of the printing press," Jeremy Bornstein , cofounder and president of Subutai, said in a statement. "We wanted to explore what the novel could be now that it's practical to use a platform more modern than paper."

Readers can access The Mongoliad through a six-month subscription priced at $5.99 or a yearly subscription of $9.99.

Stephenson is an author of several speculative fiction and science fiction novels, including Anathem, the Baroque Cycle, Cryptonomicon, The Diamond Age and Snow Crash. He also writes nonfiction articles about technology.

Bear is the author of more than 30 books, in the thriller, science fiction, and fantasy genres, including Blood Music, The Forge of God, Darwin's Radio, and Quantico. He has received two Hugos and five Nebula awards for this novels.