Amazon has released version 2.5 of the Kindle app for the iPhone, iPod Touch, and iPad. The two new features in the 2.5 release is downloading of eBooks in the background and the ability to add books from sources other than Amazon’s Kindle book store.
In my testing, I was not able to add PDF files to the iPad app, which is something that you can do on an actual Kindle. Fortunately, there are several other PDF readers for the iPad, so that not being included is probably not a problem. You also cannot add eBooks in the EPUB format, which is commonly used by libraries and other book stores like Barnes and Noble.
What you can add are eBooks in the MOBI format, AZW, which is the Kindle eBook format, and TXT (text files). The MOBI format was originally created by Mobipockets, which Amazon aquired in 2005. A source for eBooks in the MOBI format is Project Gutenburg, which is the first producer of free eBooks on the Internet.
You add eBooks to the Kindle app either with iTunes or as an e-mail attachment. I tested the capability by e-mailing to myself The Adventures Of Tom Sawyer and opening the message in the Mail app on my iPad. E-mail attachments that are compatible with the Kindle app display with a Kindle icon, and when you tap them they will be opened in the Kindle app.
I have found that not all MOBI format eBooks work with the Kindle app. The book I first tried was the version of Tom Sawyer on Project Gutenburg that includes images, and that did not load. I then tried the version without images, and it was recognized as compatible and loaded in the Kindle app.
Another issue is that the MOBI books that I added to Kindle do not have any cover art on the Kindle app home page. As you can see in the screen shot, the books don’t even have a text title, just a generic graphic for a PDA.
While it is nice that Amazon is enabling users to add eBooks from other sources to the Kindle app, I think it needs to support more formats, particularly EPUB and needs to provide some way to at least display the book’s title on the home page. Of course, the update, like the app, is free, so there is no reason to not install it.