A Kindle Boards thread clued me in to this article on how Goodreads users find books (in one case, at least).
Hey Amazon, how about making this kind of analysis available for your site? Maybe you could use a hit indie book as an example, since we self-publishers don’t have as many marketing resources as Random House.
The Active Voice 
I’ve not seen progressive analysis of a book in the marketplace like that.
Thanks for sharing this Becca : )
You’re welcome! It really is rather extraordinary the kind of data that can be gathered on these sites, huh? Maybe, in time, this kind of analysis will be auto-generated for every book. Talk about a useful marketing tool.