The iPhone may soon be able to download books made with iBooks Author. Currently, iBooks Author books can only be downloaded on an iPad running iBooks 3.0 or later, on iOS 5.1 or later. But a recent change in the requirements language on the iTunes Store may point towards iPhone compatability in the near future, according to Macworld:
While this message still shows up on the Web, visit an iBooks Author book in the iTunes Store and you’ll see the following: “To view this book, you must have an iOS device with iBooks 3.0 or later and iOS 5.1 or later, or a Mac with iBooks 1.0 or later and OS X 10.9 or later.” A request for comment from Apple regarding the wording change went unanswered on Wednesday, and as of this writing, the iPhone still can’t download iBooks Author ebooks despite the text’s claims to the contrary.
The change in language, which reflects the upcoming release of iBooks for Mac on OS X Mavericks, is a positive sign. iBooks Author already has support for portrait books, with interactive elements appearing along the side of the text as the reader moves through the book, and this view would be ideal for the smaller screens of the iPhone and iPod touch. It's extremely likely that there will be an updated version of iBooks released on iOS this fall with support for iOS 7, and it's entirely possible that this version will also bring iBooks Author support to Apple's smaller screens.