free datasets:
Free dataset downloads - The British Library
Bulk downloads, serialized as N-Triples, RDF/XML or Turtle (ttl) are available below for published and forthcoming books and serials eligible for BNB.
Dataset Repositories - Datasets at the Library of Congress: A Research Guide - Research Guides at Library of Congress
Library of Congress Releases Data for Free Download and Discovery | Library of Congress
Books Dataset | Kaggle
Firebase used to be excellent dataset, based on "semantic web" design model (RDF etc)
company acquired by Google and absorbed into search results.
The original open dataset is migrated to Wikidata, that is now main free, structured data resource.
Freebase (database) - Wikipedia
Freebase was a large collaborative knowledge base consisting of data composed mainly by its community members. It was an online collection of structured data harvested from many sources, including individual, user-submitted wiki contributions.[3][2] Freebase aimed to create a global resource that allowed people (and machines) to access common information more effectively. It was developed by the American software company Metaweb and run publicly beginning in March 2007. Metaweb was acquired by Google in a private sale announced on 16 July 2010.[4] Google's Knowledge Graph is powered in part by Freebase.[5]
Data Dumps | Freebase API (Deprecated) | Google Developers
Wikidata - Wikipedia
Wikidata is a collaboratively edited multilingual knowledge graph hosted by the Wikimedia Foundation.[2] It is a common source of open data that Wikimedia projects such as Wikipedia,[3][4] and anyone else, can use under the CC0 public domain license. Wikidata is a wiki powered by the software MediaWiki, and is also powered by the set of knowledge graph MediaWiki extensions known as Wikibase.Wikidata
Wikidata is a free and open knowledge base that can be read and edited by both humans and machines.
Wikidata acts as central storage for the structured data of its Wikimedia sister projects including Wikipedia, Wikivoyage, Wiktionary, Wikisource, and others.
Harry Potter - Wikidata
Wikidata:Data access - Wikidata
https://www.wikidata.org/wiki/Special:EntityData/Q42.json
Wikidata:Tools/For programmers - Wikidata
Google Books APIs | Google Developers
Google Books is effort to make book content more discoverable on the Web. Using the Google Books API, your application can perform full-text searches and retrieve book information, viewability and eBook availability. You can also manage your personal bookshelves.
Getting Started | Google Books APIs | Google Developers
book synopsis api from google or amazon? - Stack Overflow
ISBNdb.com: used to be free, from Amazon, not free anymore
Free ISBN Web Service | AWS News Blog (2006)
The World's Largest Book Database - ISBN Database | ISBNdb
book synopsis api from google or amazon? - Stack Overflow
Amazon: The API you need is the Product Advertising API
http://associates.amazon.com/gp/advertising/api/detail/main.html
Introduction to Books DB2 Sample Database