If you're a fan of photography, you may have succumbed at some point to the photo book addiction. It’s not a cheap habit, at $50, $75, even $100 a pop. From the photographer's perspective, having your work published in book form is a rite of passage that you've owned a topic or you’ve arrived at a certain status in your career.

The downside is that the process can be expensive for a photographer these days. You’re lucky if you find a publisher who is willing to take on the project. And even if you do, you’re often paying for that good fortune. The publisher isn’t footing the entire bill; the photographer is often fronting tens of thousands of their own dollars for production costs. But publishing for tablets is giving photographers a cheaper alternative to books.

Gerd Ludwig / INSTITUTE

On April 26, 1986, this amusement park in Pripyat, Ukraine, with bumper cars and a Ferris wheel, was being readied for the annual May Day celebrations when the nearby Chernobyl reactor blew up. Rotting away for 25 years, the contamination zone around the reactor has become a symbol of the utter abandonment of the area. Now it is an attraction for tourists who have started flocking to the area in droves.

One recent example is Gerd Ludwig's "The Long Shadow of Chernobyl" iPad app released December 2011. Some images from the app are shown here.  A long-time and well-known National Geographic photographer, Ludwig has covered the fallout of the Chernobyl meltdown periodically since 1993.

In the app you see 150 images, a book-length number. They are broken up into chapters and features on different topics. But unlike a book, you can help yourself to the material in a linear or non-linear way.

Some other photo apps are truly books ported over to app form, an adjunct to the print publication. One example is Christopher Anderson's "Capitolio," where you literally see the book page layout in the app, along with some non-print features like a video interview with the photographer.

Gerd Ludwig / INSTITUTE

Suffering from thyroid cancer, Oleg Shapiro, 54, and Dima Bogdanovich, 13, receive care at a thyroid hospital in Minsk, Belarus, in 2005, where surgery is performed daily. As a liquidator, Oleg was exposed to extreme levels of radiation when the Chernobyl reactor blew up in 1986. This was his third thyroid operation. Dima's mother claims that Chernobyl's nuclear fallout is responsible for her son's cancer, but his doctors are more cautious. Belarusian officials are often instructed to downplay the severity of the radiation.

In the case of Ludwig's app, his team worked with Lisa Lytton, who spent years in both magazine and book publishing and then started Lightbox Press, an app publishing company. I asked them if their project was a book or an app. Both said this experience changed their thinking -- it goes beyond a book to thinking about interactivity. 

Gerd Ludwig / INSTITUTE

The city of Pripyat, Ukraine, once inhabited by 50,000 residents and brimming with life, now stands as a chilling ghost town. Built in 1970 for the scientists and the workers of the nearby Chernobyl nuclear power plant, authorities did not warn residents of the April 26, 1986, accident, and only issued an evacuation notice two days after the explosion.

Ludwig and Lytton’s app includes panoramic images and video. One video lets you experience a trip deep inside the destroyed reactor. Ludwig has gone deeper into the reactor than any other Western still photographer, so deep in fact, that his photo assistant refused to go in with him for fear of the radiation exposure. Recorded with a Go Pro camera mounted to his head, you hear what he calls the nerve-wracking beep of the Geiger counter checking his radiation exposure as he wound his way with work crews through the dark tunnels and rooms of the reactor.

Lightbox Press

The app as seen on an iPad.

Ludwig has published a book before, but he said he appreciates the app for enabling him to tell the story in a more complex way than a traditional book. The app tells the story both about the subject and the experience and process behind the story, transparency that’s not always possible in a traditional book.

While they spent dearly in time and staffing to organize the material for the book, there was no big upfront production fee. Both Ludwig and Lytton are gambling on a new business model, hoping to recoup their expenses through sales of the $6.99 app.

Will that business model work? I asked Greg Harris, co-founder and creative director of Daily Interactive. His company created an app for Michael Nichols' wildlife photography and released it last summer. The goal of the app wasn't to create a photo book in app form, but to replace a web site and monetize the content. He says the key to success with apps is making sure consumers know the content is available. "It all depends on marketing to drive downloads. They are doing well but not “Angry Birds” well.”

When I asked Ludwig if he had a personal connection to the Chernobyl story, he said it hit home for him when he called home to his native Germany and heard of friends who sent their children or pregnant relatives to Holland because the radiation cloud was moving into southern Germany.

Ludwig plans to continue covering the story he started almost two decades ago. He said the story of the geography and people of Chernobyl continue to resonate because it will always be the first huge nuclear accident. He hopes it will be the last.

Gerd Ludwig / INSTITUTE

In 2011, a quarter-century after the Chernobyl nuclear accident, books decay and paint peels in a school library in Pripyat, Ukraine, once the area's largest town with 50,000 inhabitants.

Learn more about the app "The Long Shadow of Chernobyl." (An Android version is not available)

Related story: Chernobyl experts hopeful on Fukushima

Gerd Ludwig / INSTITUTE

Initially branded as illegal residents, a few hundred elderly have returned to their village homes near the Chernobyl nuclear disaster site. Now tolerated, but without means of transportation, the returnees have no easy access to medical help. To ensure basic health care, teams of doctors from the Chernobyl hospital make their rounds to the few inhabited villages each month, shown here in Ilyintsy, Ukraine, in 2005.