Well, I looked through the files a bit more in the app, I think I can probably take a stab at a start, but not sure how far I'll get. The full books are all listed in the attached xml file. Downloaded samples don't appear in the xml or any other support files for some reason, possibly because they don't have DRM. The filename of the book is the ASIN id plus an extra static extension. So It should be relatively straightforward to parse the xml to show the current books on the iphone.
The big issue is that the iphone doesn't mount as a proper usb disk/filesystem. There are a few filebrowsers that let you access the system using some special tricks, but I don't see a cross-platform library doing this.
I think for now I'm going to try out an approach where I share the filesystem over wifi using Netatalk
. It allows you to create an AFP share from the iphone.
If it helps I could post the whole kindle.app directory sans paid books.