I applaud the effort, but last time I tried this the major issue was the sheer amount of book data only available from amazon.com and scraping that is tedious to put it mildly.
I'm hoping Goodreads and Anna's Archive will help fill in the gaps, especially since Anna's Archive have gigantic database dumps available[1].
In fact, now that I think about it, you could also contribute your work to WikiData. I don't see ISBNdb ids on WikiData so you could write a script to make those contributions. Then anyone else using WikiData for this sort of thing can benefit from your work
I’d love to help improve other services. I plan on charging for Librario at some point, but I’ll offer a free version and offer free API keys for projects like Calibre and others.
At least that’s the plan.