It's very configurable and extensible. As some have mentioned, the interface can be a bit confusing at times but once you're used to it it's mostly out of your way. I like that I can run it on both my Kobo and android phone and sync progress. I also self host an opds server but you can also connect to calibre, syncthing, or cloud storage to pull down books. There's even a plugin to sync my progress to hardcover, which is a more open alternative to Goodreads.