A year ago, when we began to review iPad apps, an apparently unassuming little book called Bartleby's Book of Buttons struck us as one of the best story apps available in the then-infant market.

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We were captivated by the story of this button-collecting gentleman because it actively engaged readers in advancing the story through the technology. It didn't just give them a story with interactions to play with. "It’s remarkably different in look, tone and structure from most story apps, a true original in an App Store filled with cartoon tie-ins, princess programming and retrofitted children’s classics," we said. Then we waited eagerly for volume two.

We were not disappointed. The Button at the Bottom of the Sea, we were relieved to see, maintained the disarmingly appealing retro vibe of the first volume while also expanding on its interactions in ways that keep the experience fresh and exciting. The secret to these books' success? The remarkable collaboration between Honolulu-based authors Henrik and Denise Van Ryzin (Henrik is the illustrator, too) and Seattle-based developers Kyle Kinkade and Nate True of Monster Costume.

From the beginning, Bartleby was conceived as a story unique to the tablet medium. The idea took root when Henrik Van Ryzin saw Steve Jobs’ presentation that introduced the iPad to the world. "I remember thinking that this opens up so many possibilities for storytelling,” he says. “I wanted to rethink the way stories are put together."

"One of the appeals that made us [at Monster Costume] want to make Bartleby was that it crosses the line between game and book,” Kinkade adds. “But more importantly, [it] is a level of interactivity in a children's story that could only exist on a multitouch device such as the iPad."

But where the relationship between creators and developers began typically—the Van Ryzins had been working with Monster Costume on another project and went to them with Bartleby—the line between the two became so blurred with The Button at the Bottom of the Sea that the collaborators now see themselves as one creative team, with story and illustration ideas both informing and being informed by the app development.

"I board out a conceptual story arc with proposed button actions, and we run through the book in a big team meeting,” Henrik says. “At this point Kyle and Nate are able to suggest things that I had not considered, and we rethink the story and how the interaction affects it.”

Denise Van Ryzin adds, "Henrik and I don't know anything about coding. And sometimes our ideas push Nate and Kyle to make something totally different and new. And sometimes their ideas make us go, 'Oh yeah! Wouldn't that be COOL?!' "

Cool it undoubtedly is. From the option to use Apple's AirPlay feature to broadcast the app's action on a TV, which turns the iPad into, literally, Bartleby's book of buttons, to a basketful of "Easter eggs" that will keep poking fingers busy for months, to a range of interactions that challenge readers young and old, it is one surprising app.

Henrik and Denise have experience in the world of educational apps, and the team takes care to field test it every step of the way with children. "Our kid testers do a great job of playing it at least one page at a time, which is good for usability,” Kinkade says. “I think honestly it's very humbling to have a 4- or 6-year-old tell you, 'This page is boring,' and force you to think of what you can add."

Predictably, children have an easier time with the app than their elders. "We get most of our 'I'm stuck' e-mails from grandparents,” Denise says. “Usually, if they give the iPad or iPhone to their grandkids, they solve it in seconds.”

Interestingly, everyone on the team refers to the Bartleby apps as "books" without hesitation. Kinkade says that they've heard from people that what children do with Bartleby isn't really reading, "but ‘book’ is the closest word. We're defining a new medium here, so we have to work with something."

They may not be on paper, but both books harken back to traditional print, from the consciously Tintin-esque illustrations to the "To Be Continued" at the end of The Button at the Bottom of the Sea. "As a young reader," Henrik says, "I always enjoyed a good cliffhanger."

Fortunately for those children and adults on tenterhooks for Bartleby 3, the team swears it won't be as long in coming as volume two was. And there's plenty more of the "Buttonverse" to explore. For those wondering what shape stories will take in the future, the Bartleby series serves as a damn good model.

Vicky Smith is the Children's and Teen Editor at Kirkus.