In April, 2011 Google implemented the Google Panda filter which fundamentally changed Google SEO.
In the old world, google assessed the quality of the site - looking at tags, links, content and other site based metrics.
In the new world, google assesses the user experience - looking at what your users actually do when they come to your site.
This is a fundamental shift that, if you don't make immediate and meaningful changes to your site, can take you from a well-ranked site to not showing up at all for your search terms, overnight.
Pick up this book and learn about the changes and how you can make a few simple changes to your site and your SEO approach to survive and thrive in the New Google Search.