I was referring to digitizing books as Luis defines it - actually typing in the scanned pages. Not the scanned pages themselves, as Google Books had.

My comment was regarding reCAPTCHA not being used to convert scanned book pages to text.

For books older than my mom, most of which must be public domain, there are a lot online archives. In fact, some of the more common archives like Project Gutenberg, are available as free ebooks on Kindle and iBooks. For more obscure titles, there are field-specific archives from where Google accessed them.

They only got information from publishers and archives. So information you're looking for is out there somewhere in digital form.