Google Books can yield important genealogical information. 
Jim Owston includes some hints on how to maximize Google Books search results on his blog at http://linealarboretum.blogspot.com/2010/10/genealogy-by-google-books.html
James M. Owston, EdD is Dean of Online and Individualized Learning Associate Professor: Communication & Media Mountain State University PO Box 9003 Beckley, WV 25802-9003
Take a look at this piece as he offers some really good tips.
I have found a tremendous amount of genealogy information from Google Books. See my blog about Google Books and Genealogy. The blog is about how to structure some queries using the Google Books search engine and some of what I found.
Regards, Jim