I was interested to see this note on the home page of Google Book Search:
It links through to a page of 'research tips' based on the use of Google Book Search.
Can't remember where you found that quote? Did someone grab the last copy of the book you needed from the library? Google Book Search can help! [Research Tips from Google Book Search]
It is nice to see it mention the Worldcat link ...
I note that it does not mention Google Scholar.
Aside: a search on 'book' in Google returns Google Book Search as the first result.