I do with Dropbox too, along with a portable version of Calibre. For syncing to my andoid phone, I use [Calibre Companion](https://play.google.com/store/apps/d

I do with Dropbox too, along with a portable version of Calibre. For syncing to my andoid phone, I use [Calibre Companion](https://play.google.com/store/apps/details?id=com.multipie.calibreandroid https://play.google.com/store/apps/details?id=com.multipie.c...).