In Windows Kindle you can load mobi books to documents\My kindle content. in android you can sideload by copying the mobi books (with astro file manager) to /mnt/sdcard/kindle. In the Metro kindle app i downloaded 2 free books from the kindle store but couldnt locate the folder that keeps the book files. i did find 2 folders program files\windows apps\kindle~~~~~~~ and users\user\appdata\local\packages\kindle~~~~~ (you have to take ownership before it will let you into those folders) but no sign of the downloaded books. Can anyone here help? (i know i can use the old Kindle Windows app, but it's not very touch friendly, and it has some issues)
+1 to the failure list. I've had a good snoop around (tbh the appdata\local\packages\ folder is the only one you can freely write to, I thought) but I can't see it anywhere. I even disconnected my network to prove it was an offline book.
I've looked into this a bit further. I found the app's code and it's actually written in javascript (seems like a surprisingly large number of the apps are, so far). So I looked through the code, and I guess fairly obviously, it uses the browser's local storage facilities (that's an HTML5 feature, right?) for the data of a custom written database (js...over 100kb of code for that alone). All of that code is modifiable so you could probably change the kindle app to add a side-loading option
As far as I know, apps can use JavaScript of HTML5 as an interface with the Start Screen. The apps themselves can be coded in other programming languages and use JavaScript or HTML5 as a shell (essentially), but depending on what the app does there may be no need for other languages to be used.
Changing the app will not be possible, as it requires a signature. Also, I believe that the app uses some sort of winRT local storage API, not a anything standards based.