See the following for more information:
Calibre Documents Provider

calibre Content Server

As many eLibrary Manager users are likely aware, calibre is a desktop application for eBook library management. For those not familiar with calibre, you can find out more at calibre - Help. One of the features that calibre provides is a content server for making books in your calibre library available through a browser. Calibre Documents Provider provides a means for Android applications to similarly access remote book files through the calibre Content Server.

Calibre Documents Provider

The Calibre Documents Provider application extends the Android platform to allow access to eBooks through your calibre Content Server. Using the standard Android Files application, you can browse and access remote books files just like you access files that are loaded on your device shared storage.

With the eLibrary Manager application installed, you can also use that tool for accessing remote books, giving you all the capability to explore and read books without actually having those books loaded locally on your device.

Important Note: By default, network access is enabled over WiFi (and Ethernet) only. If you enable access using mobile cellular data, be aware that scanning and reading remote book files can use significant amounts of data since those actions involve streaming book content. Also, this application is primarily intended for access to your calibre Content Server in a private local network. If you are accessing the Content Server over the internet, then be aware that book streaming will count against internet data limits as well.

Some of the things you can do with this component are