This is awesome. Exactly the sort of thing I like to see on HN: someone going deep on a niche they really care about. The app is more polished than I expected.

The design is nice and clean. I really appreciate dark mode as well, though some of the text on this page, for example https://app.librari.io/subscription looks like it needs to be tweaked for dark mode.

I would genuinely use this, as I don't always like the public aspect of Goodreads, but it would depend on your pricing structure and privacy policy.

Feature request: bulk import of books.