Photo books aren't exactly "in," but Mixbook's Caleb Elston is convinced that physical keepsakes are going to make a comeback, thanks to intelligent creation tools on smartphones. "There is something powerful about turning digital bits into physical atoms," he says, and he might be right. Apps like Postagram have had success offering cheap postcards you can make on a smartphone, and companies like Facebook are pushing users pretty hard to order IRL gifts for friends. Mixbook today is launching Mosaic, an iPhone app that lets you create and order a photo book in less than five minutes. Now that iPhones are consistently the most popular cameras on Flickr, iPhones might just be the place to start building a photo book.

"Since we take so many photos on our phones, each photo is independently less valuable than if we had a camera roll."

Before he was Mixbook's Director of Mobile, Elston launched Yobongo, an iPhone app that let you instantly chat with strangers in your neighborhood. Yobongo was dead simple to use, offering a bare bones way to communicate with others with hardly any settings to fumble around with. Mixbook, which looks like a site your grandparents might use, acquired Yobongo to help create a sleek mobile experience, and to that extent Elston has succeeded. "We realized that iPhone photos are high enough resolution to print well at 5 or 6 inches at 300 dpi," he says says. "But since we take so many photos on our phones, each photo is independently less valuable than if we had a camera roll." Thus, the Mosaic photo book was born, operating on a similar level of simplicity as Yobongo. The value lies in the fact that the book isn't a Facebook album filled with hundreds of photos. Mosaic only asks you to pick 20 photos on your iPhone, choose a black or white background, and shuffle around the photos in the trademark "mosaic" book cover if you'd like. You're left only with your photos, set in stone (or paper, rather).

Mixbook prints out a 7-inch photo book ("just right," according to Elston) and mails it to you within four days. As your book makes its way through the ether towards your front door, the app pushes you shipping and "out for delivery" notifications. The entire experience really couldn't be simpler, but in a world where people are becoming more and more accustomed to purchasing digital goods, Mosaic is a big risk. Elston's betting on Mosaic as a way to memorialize a fun weekend or party you had, and not as something you'll spend hours working on, like many Mixbook customers do on the web. "In the end, you have something of high value," he says. "The medium changes your experience. A physical book changes your response to your photos." Twenty dollars (plus $5 for shipping) is a lot to ask from millions of iPhone users scared to even spend $5 on an app they'll use for months, but if you're up for it, there's no simpler way than with Mosaic.