I'm looking for a Kindle app replacement for my phone and Kindle Fire, ideally one that can get my Amazon books if possible.
I want to be able to add books through Calibre, and sync them to the furthest page read on all devices, and I want to be able to store all my books without the app removing them.
FBReader might be an option. You can upload books using the FBReader Book Network, which uses your Google Drive as storage, and then use it to access your books and synchronize your progress across a variety of platforms.