Camera+ is a well-regarded $1.99 iPhone app that modifies photos right on the iPhone. The current version of the app has a quite remarkable 4.5 average customer rating based on 2,103 ratings. The publisher of Camera+, taptaptap, points out a book of photographs based on a trip through Italy. All of the photos in the book were taken using Camera+ on an iPhone.
The book is a self-published one (using Blurb.com). However, this is merely a technicality that I wanted to mention. Based on the photos that taptaptap pulled out for their blog, it looks like a book of remarkable photographs. It is quite amazing to note that all the photos are from an iPhone.