(Taken from the Developer)
BookShout! is the first app, currently available on the iPhone and iPad, that allows users to share comments back and forth with other readers in your circles. There is no other technology like this out there yet, and best of all, it is free to use!
BookShout! is a social reader app for readers and writers of Christian books. It's like a Kindle meets Goodreads. I downloaded the BookShout! app on my iPhone, and found it to be similar to the other e-reader apps I use. On the website, http://www.bookshout.com, you'll find free downloads as well as extensive categories of interest. The site and app are simple to use, and the social features are pretty cool. Like Goodreads, you can see what your friends are reading, and join groups to discuss books and common interests.
If you've got an iPhone or iPad, and you want a large selection of Christian authors to choose from, check out BookShout!