books
Open Library
An open, editable catalogue of books, editions, and authors run by the Internet Archive, holding records for over 40 million editions and works, with links to borrowable copies. You can search by title or look up a specific ISBN through its keyless API, or browse the catalogue on the web. It is a solid general-purpose stop for bibliographic details and for finding where a book can be read or borrowed.
Why it’s useful & how it works
The HTML homepage was 503 (overloaded) but the JSON APIs (search.json + books) answer 200 both ways. No key; set a descriptive User-Agent to avoid rate-limit blocks. ISBN/OLID lookups are tiny JSON.
What’s inside
~40M+ editions/works.
API access
https://openlibrary.org/api/books?bibkeys=ISBN: <isbn>&format=json&jscmd=data ; search https://openlibrary.org/search.json?q= ...
Access
Programmatic API access (a key may be required — see the API tag).