You can choose one or more of the following book databases in the Settings:
- Open Library (API, recommended)
- Google Books (API, recommended)
- Europeana (API)
- Library of Congress (API)
- Amazon (scraping - slow)
- Goodreads (scraping - slow)
- Boekwinkeltjes.nl (scraping - slow)
- Bol.com (scraping - slow)
As soon as a high confidence match is found, the search is stopped. In case of equal scores, the result that has a cover image is chosen.
Europeana is a good source for historical/European works. Library of Congress is best for U.S.-published books, especially academic, nonfiction, and trade books.