Having been a long-time user of Kindle and Nook, I end up using Google Books most of the time, here are some reasons:
- Amazon Kindle does not support ePub which is a most common format
- Barnes and Noble Nook does not allow to upload new books to the cloud and from there to the Nook via WiFi
- Only Google Books allow reading the text using the Android system voice (TTS)
- For Google Books adding newly purchased books is as simple as clicking "Upload files"
To manage my eBooks I use: