Google has released their estimate for the number of books: 129,864,880.
They also offer a full explanation of their counting methods, with some interesting quotes:
- “we can’t rely on ISBNs alone is that ever since they became an accepted standard, they have been used in non-standard ways. They have sometimes been assigned to multiple books: we’ve seen anywhere from two to 1,500 books assigned the same ISBN.”
- “We trust OCLC and LCCN number similarity slightly less, both because of the inconsistencies noted above and because these numbers do not have checksums, so catalogers have a tendency to mistype them.”
- “We tend to rely on publisher names, as they are cataloged, even less. While publishers are very protective of their names, catalogers are much less so. Consider two records for “At the Mountains of Madness and Other Tales of Terror” by H.P. Lovecraft, published in 1971. One claims that the book it describes has been published by Ballantine Books, another that the publisher is Beagle Books. Is this one book or two? This is a mystery, since Beagle Books is not a known publisher. Only looking at the actual cover of the book will clear this up. The book is published by Ballantine as part of “A Beagle Horror Collection”, which appears to have been mistakenly cataloged as a publisher name by a harried librarian.”
I’m not a cataloguer, so I’m not the best person to critique all of Google’s assumptions (perhaps Tim Knight or others can chime in on the accuracy?). However, I do find it interesting that Google is willing to leverage the tedious hours of work by Librarians, and then turn around and offer disrespectful tone to every human mistake.