I built a little Jellyfin plugin for KOReader [1] so I can access my books from my Kindle. Jellyfin proved really nice to work with (though there was some poorly documented auth stuff they were in the process of deprecating).

If anyone has been thinking of building something in the Jellyfin ecosystem, I very much recommend it.

[1]: https://github.com/DeclanChidlow/KOReader-Jellyfin-Plugin/