PageFlip 3D Book SDK is the easiest way to create a custom story book (like a children's story book or a browsable brochure) for iOS platform (iPad or iPhone/iPod). All you need is high resolution graphics images. Just place those images into a template, save as JPGs, insert them into XCode project and you're ready to submit to AppStore. The advantage of this technology over iBooks is that you get the full source code and you can customize your book in various ways: make book interactive, add original effects in Open GL, add customized animations and games.
Example Xcode project comes with all necessary Photoshop templates to publish your book. Check out the demo project on AppStore and you basically get the full source code to it.