Amazon.com has a feature called Statistically Improbable Phrases (SIPs) that has been around for about 5-6 months now. I found out about it today. Ouch!
(If you didn’t already know of it, you found out after me ;-) )
Basically, an Amazon SIP allows you see the most common phrases in a specific book, MINUS those that are also found in other books searched/indexed by Amazon. So you get the most unique phrases in book and are guranteed that it makes some sort of sense because the author repeated them so many times in his book. Also, as other authors haven’t repeated this phrase enough times, it retains the uniqueness to that specific book.