I use Calibre to manage my ebook library. I share it across devices (and with a couple friends) using Syncthing[1], and read the books using KOReader[2] on a Kindle. I get my books either from Z-Library or by ripping the DRM off of books purchased from Amazon.
Genuinely the best reading setup.
[1]: https://syncthing.net/ [2]: https://koreader.rocks/