In the debate over Google Book Search there’s always discussion over the usefulness of limited pages, people reading online, copyright and whether there’s even a point. I’m of the camp that thinks it will be a great achievement. For those wondering about whether such a thing would help sell books here’s a real-world example (using Amazon’s offering):
Semco: The Success Story Behind the World’s Most Unusual Workplace - Signal vs. Noise (by 37signals)
From the comments there appears to be a few purchases.