Calibre vs Librum

Calibre and Librum are both free, open-source programs for managing digital libraries. They support various book formats (for reading and parsing metadata), allow to organize books by various parameters, sort and filter collections, search by metadata and book text and support plugins and extensions.

However, Calibre is a regular desktop software for Windows, Linux and Mac with much more functionality. It supports more book formats, audiobooks, has a built-in format converter, local server for remote access, syncs with e-readers and updates metadata from the internet. However, Calibre's interface is overloaded and it's more difficult to use.

Librum is available in two versions: a free, open-source server that can be installed on a desktop (though this requires specialized technical knowledge) or an online service. The online service also has a free version, but it is severely limited in cloud storage and increasing it requires a small monthly fee. Also, if you use the online version, you'll have to constantly upload/download books, which takes time. However, it's more simple and convenient program with a more modern web interface and high speed. Another advantage is the ability to use built-in AI to explain, summarize books or provide some context information.