@mst: you need to understand the differences between a file manager and a library.
A library is what Kobo OS (aka nickel) and calibre use for books. They store books in a database.
A FM is what KOReader uses. Books are no different from other files here. They are just "normal" files within the filesystem hierarchy.
KOReader has some plugins that extend the FM. The most important of them is named "CoverBrowser" and allows you to see book cover and metadata for the current directory. That plugin uses a database internally, as part of the plugin, but
was not intended as a library feature.
Other plugin that KO has is "calibre", which allows you to transfer books wirelessly
and search book metadata. The kind of metadata this plugin parses is explained in
https://github.com/koreader/koreader...data.lua#L4-L6
That's it. Patches welcome to implement a "library app" or "library plugin" that behaves like nickel or calibre. Until that happens you're tied to a file manager and some enhancements on top of it.