Books are different from the web, but Google is trying to find ways to make its book search tool as effective as its web search engine.
Rich Results is the latest in a series of smaller front-end tweaks that have been matched by backend improvements. Now, the book search algorithm takes into account more than 100 "signals," individual data categories that Google statistically integrates to rank your results. When you search for a book, Google Books doesn't just look at word frequency or how closely your query matches the title of a book. They now take into account web search frequency, recent book sales, the number of libraries that hold the title, and how often an older book has been reprinted.
