In the past couple of years there had been a bit of rumbling about Google's project to scan and index published books for search. I believe there were even some lawsuits about it.
I am a bit of an extremist, in that I believe that organizations such as Google are wrong to believe that, unless otherwise excluded, they have a right to search and index published content. I believe that as a copyright holder, companies such as Google need to get permission before cataloging and storing my content. I don't dispute that search engines are beneficial; but I believe the onus is on the searcher to obtain permission and not on the copyright holder to deny it after the fact.
So, that's my disclaimer about my beliefs. Now, as to how Google's book search benefits authors and publishers:
Last week I was Googling for information on how to set up dynamically mountable user directories under Linux. Of the articles Google presented to me, their scanned copy of Oreilly's "Linux Server Hacks, Volume Two" had the most clear and concise explanation. I could very well have set up this functionality with the Google results alone; but the Google preview of this book introduced me to a book that would be useful to me on a regular basis. So, I ordered it from Amazon and it was just delivered.
Score one for Oreilly choosing to have their books indexed by Google.