https://github.com/janeczku/calibre-.../G-Drive-Setup

Calibre library (metadata.db) can be located on a Google Drive. Additional optional dependencies are necessary to get this work. Depending on your type of installation install the dependencies via pip install calibreweb[gdrive] or for the manual installation install the dependencies by executing pip install --target vendor -r optional-requirements.txt

To use Google Drive integration, you have to use the Google Developer Console to create a new app. https://console.developers.google.com.