How can I find out whether a book is available online?

Millions of e-books can be found, often with a direct link to full text, via HOLLIS.

Leave search tab on Everything.  On the results page you will see a box at the top of the column to the right of the results list labeled Show only; select Online. Then go down the column to Resource type and select Books. These include the holdings of the largest e-book collections, including Hathitrust, Google Books, the Internet Archive, and Project Gutenberg, as well as Harvard's own digital collections. HOLLIS searches information about items (i.e., metadata such as title, author, publisher, subjects, etc.), not the full texts of the items.

Important  sources for e-books which may not necessarily be included in a HOLLIS search are:

WorldCat, a collective catalog for more than 72,000 national, academic and public libraries, primarily  in the United States, but including those in 170 other nations.

To find digital books in WorldCat, click on the Internet Resources tab on the results page to limit to e-books.

The search will retrieve both public-domain texts that are freely available, but also subscription resources available only through purchasing libraries. This database is particular useful for finding European digital texts.

Europeana provides access to the holdings collections of 49 European National Libraries and other university and research libraries.

The catalog of the Digital Public Library of America provides a valuable interface with its growing collections of e-books and archival materials.

Wikipedia entries on authors and particular works sometimes provide a section of External Links at the end of the entry, including links to online archives and full-text versions of books. In addition, their List of digital library projects may help uncover specialized, regional, language collections which may contain some relatively obscure items not found elsewhere. See also the University of Pennsylvania’s Online books page for additional e-book resources

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