Search engines that specialize in books such as BookFinder.com or WorldCat.org allow readers to search for a book regardless of whether or not they remember the title. Readers may also use Amazon.com's Search Inside! service if they wish to purchase books on Amazon.com.
BookFinder.com indexes more than 150 million books as of 2015, including books that are rare or out of print. Readers who forget the title of a book may search for it using information such as related keywords or publishing year.
WorldCat.org is the world's largest online network of libraries and library services. Readers may search for books using data such as keywords, publishing year and the recommended audience in addition to the title and author. Readers may also search for other media such as CDs and DVDs.
Search Inside! is a book search engine provided by Amazon.com. This search engine is unique because it allows readers to search for a book using a quote from the text. Search Inside! compares the quote against thousands of books until it finds a match. For each match, Amazon.com displays the page number. Clicking this page number allows customers to view the actual pages where the quote occurs using Amazon.com's online reader.