Hi there,
have you already heard of
eBook Searchr, a new e-book search machine based on Google's Custom Search Engine technology?
The search machine scans more than 100 selected ebook sites, which all contain free e-book downloads. Non-ebook sites will not be considered, i.e. only the relevant sites will be found (contrary to a normal google.de search). You get the best search results if you enter the complete title of the book, e.g.
“Harry Potter and the Deathly Hallows”
Best regards,
chunky bacon
http://ebooksearchr.googlepages.com