"There is another city, and it might be a millennium old, or merely an hour. It coexists with your own, bridging the soft places, blurring rigidity and permanence... This cannot hold... As each manifests, one city must fall. One city will burn and these pages you write will fall like ash."

An academic and an artist have hidden Raspberry Pis across Bristol (UK) that transmit sections of narrative to readers hoping to fill in the blanks of an offline book.

The project, These Pages Fall Like Ash, is headed up by academic and Pervasive Media Studio resident Tom Abba and artist Duncan Speakman. The story is a tale of two cities, one being the reader's physical surroundings in Bristol, the other a second city that cannot be seen—a kind of parallel universe that coexists with the physical.

Participants are all supplied with a beautifully crafted wood-bound notebook, in which they will find two tales—one tracing the fictional city, the other describing the city in which the reader resides.

The narrative follows two people who once knew each other, but now appear to have forgotten the other exists. One lives in the parallel city, the other may live in your city, or be caught somewhere between the two. It's a story that uses the physical, the digital, and a reader's comprehension of the two to join the dots between those worlds and finish the story. Speakman refers to it as "haunting a place before you've seen it."

The writer has left blank spaces in his tale for the reader to either fill in or source in hidden pockets across the city, with smartphones or tablets picking up a network from the 15 hidden Raspberry Pis when they come into range. As the line between the physical book and the digital material blur, the reader becomes the mediator of that line, controlling it, adding to it, and eventually leading it to its conclusion.

"E-books are incredibly convenient and portable, but we lose that sense of a relationship with a physical object," Abba told Wired.co.uk. "We wanted it to feel like it was something you owned, that you took away with you—your journal, diary, companion throughout this two-and-a-half-week story experience, and that's critical. There's something about not just making this work on digital devices, but making the interplay between the physical and the digital a key part of it so that we felt we were guiding an audience into a space."

Abba and Speakman are one of eight groups that were awarded a React Hub R&D grant to research and trial different ways of combining digital and physical storytelling. As such, Abba sees this very much as an experiment—we're so early on in our understanding of how these two worlds can converge in a satisfying way to improve our experience of reading. One project uses the GPS in smartphones to enrich tales of train travel, while Jekyll 2.0 plans to use biodata.

These Pages Fall Like Ash launched in Bristol on April 20 and will run to May 8, with the story told across three acts. It is, says Abba, a throwback to serialized fiction of Dickens' day. This time, though, it's the Raspberry Pis that are releasing each installment, not periodicals.

"Content gets released every few days basis in geographically located chapters," says Abba. "We're asking people to use two platforms, a physical notebook and digital device, so it will be interesting to see how will they read between the two. Can we make the two interact? The experience as it rolls out is very much site-specific and located around the city. Readers use a map inside the notebook that describes where they should be standing. We're not just asking them to go to a castle or a park—there are things about the place that are pertinent. These two cities are overlapping and interacting."

The project has already been running for a few days, and so far people have taken to the interactive portion with ease, uploading data to complete the story as well as using pencil and paper to fill in the gaps. "We've had poetry written in response, photos taken [apps like Hisptamatic are used to upload these], and the books are in use."

This is important, because by act three, readers are expected to take part. "The first act gives them training wheels—the storytelling, how we're going to get content, and how we think they might read it," says Abba. "Then the more our readers engage, our question is will they contribute into act three and will that work? The resonance of how it works in storytelling is entirely down to the audience and what they give us. We think we've written the experiential parts in a way that will invite contribution, but it's a close-your-eyes-and-see moment. It opens out what we'll do next. Everyone's tried to figure out what the grammars of this kind of storytelling might be—everything really is a controlled experiment."

Abba is very much of the mind that the adventure Dungeons and Dragons-style novel is not the path to take. They want the readers to seamlessly start interacting, manipulating, and finally leading the story—while retaining "that shared space between the author and the reader where the reader imagines" rather than simply being presented with jarring yes and no options.

Abba is interested in exploring people's' relationship with the city in which they live. Having moved to Bristol 21 years ago, part of it for him is about recapturing that moment when everything is new, that sense of discovery and excitement.

"It gets people to look at their city in a different way—how it works and how they interact with it. It gets them to see things they've never seen before, and imagine things they've never seen before. We walk around with our map and smartphone and can find out where we are within five meters. That sort of closes down [our relationship with the city], but can also open it up. It depends on the type of content we engage with."

This is what These Pages Fall Like Ash is trying to achieve—to find the right balance to engage with that physical and digital world in a way that enriches the experience of reading, not hampering it in any way and not simply mimicking how we traditionally read, as e-books do.

"If you look at stage versions of films, any good adaptation looks at the heart of the text and asks 'what's the text trying to do and how's it trying to communicate?' And one of the really interesting things about working in digital is that we are figuring that out, in a very, very broad sense."

There are plans to translate the finished version online, but whatever participants penned in their notebooks remains their own private piece of the tale. If all goes well, we can hope to see Abba and Speakman take over London, New York, and beyond.

You can still catch up with the story if you sign up by April 29, with the third act coming to a close on May 8.

This story originally appeared in Wired UK.