In my experience and opinion, Google Books is designed to be overly paranoid about the spidering issue. I can spend 15 minutes there searching for interesting books without even downloading hardly any of the them, and then Google goes into paranoid mode, and starts requiring "Captcha" on everything I do. Also, the search algorithm, whatever it is, is bizarre. One day I can find a particular book, I come back the next day and enter the same search terms, and suddenly Google Books can't find it any more. Having said that, I find I can usually live with a Google Book that I find and am interested in -- either in the PDF format or the EPUB, it depends -- assuming I can't find a PG version of the book where a real human being has fixed the scannos! Someday maybe I'll even learn to live with the occasional thumb that shows up in my books! Certainly it is cool the ancient and obscure things one can find on Google Books. Not clear their efforts are really overall to the long-term benefit of society however. And there is a general problem that the more residual benefits citizens find in old books, then the more likely our "representatives" will take away our constitutional rights to read and share old books, and "sell" those rights back to ebook retailers like Google -- as has already happened in the millennium copyright laws, and/or DRM.