Assuming your phone is Android and your Kindle books aren't DRMed, KOReader.
Oh wow. It supports Kobos as well. Gonna have to check this out. Thanks.
Thank you :)
Or. LibreaReader https://github.com/foobnix/LibreraReader
It looks good, thanks :)
It's such a great app, helped to increase my reading time. You if can afford it, you should pay for the pro version.
Would Calibre Web fit the bill maybe?
I didn't know it was a reader, I thought it was just a backend. I'll have a look into it, thanks :)
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.
The Android version of FBReader has been closed-source for a number of years now.
It looks interesting, but I don't know if I've got enough space on my Google Drive. I'll have a look into it though, thanks :)
If it's free and open source and it's also software, it can be discussed here. Subcommunity of Technology.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.