Ok so I downloaded an azw file from libgen (don't judge me, it was extremely expensive otherwise). I don't own a Kindle, but do have the app on my laptop (Windows 7), and it runs great. Recently I thought I would read it on the metro while traveling, so I downloaded the Kindle app for WP. I have Lumia 635 running windows 8.1. But no matter how many times synced or reinstalled the app, I could not see that book in the app. So I downloaded the book again from libgen, but this time on the phone. Except that I cannot open it. I can see the file in the downloads folder with the 'Files' app on the phone. But unlike the laptop, I cannot open it using the Kindle app cuz I am not given an option t browse for programs. It presents me with 2 options, download an app to read the file from the marketplace, or just close it. How do I open or send this file to the Kindle App on my phone? Also, why isn't the book already in the phone app since it is registered using the same id as in the laptop?? Please Please help!
Alternatively, with mild hacks, you can gain access to the Isolated Storage of the Kindle app and just copy the file there. The app is perfectly capable of opening books copied to its storage, it just doesn't provide any way to do this.
The easiest way, if you have a microSD card, is move the app to the SD card using Storage Sense. Then, remove the Hidden and System attributes from the D:\WPSystem directory (you can find several apps that will "unhide WPSystem" on the XDA forum for hacking WP8). Finally, you can use any file management app (I like Folders Pro or Aerize Explorer, both of which are on the Store) to copy the file into the Kindle directory of the app (the path is something like
D:\WPSystem\AppData\48195fb4-ee0e-e011-9264-00237de2db9e\Local\kindle\). When you launch the Kindle app, the book should be there!
The Kindle app only supports reading books from your Kindle library on Amazon. You should be able to use the Kindle Personal Documents Service to send it to your Kindle library, and onwards to your phone (or other readers)