In December 2009, Google began customizing its search results for all users, and we entered a new era of personalization. With little notice or fanfare, our online experience is changing, as the websites we visit are increasingly tailoring themselves to us. In this engaging and visionary book, MoveOn.org board president Eli Pariser lays bare the personalization that is already taking place on every major website, from Facebook to AOL to ABC News. As Pariser reveals, this new trend is nothing short of an invisible revolution in how we consume information, one that will shape how we learn, what we know, and even how our democracy works.

The race to collect as much personal data about us as possible, and to tailor our online experience accordingly, is now the defining battle for today's internet giants like Google, Facebook, Apple and Microsoft. Behind the scenes, a burgeoning industry of data companies is tracking our personal information to sell to advertisers, from our political leanings to the hiking boots we just browsed on Zappos.

As a result, we will increasingly each live in our own, unique information universe-what Pariser calls "the filter bubble." We will receive mainly news that is pleasant, familiar and confirms our beliefs-and since these filters are invisible, we won't know what is being hidden from us. Our past interests will determine what we are exposed to in the future, leaving less room for the unexpected encounters that spark creativity, innovation and the democratic exchange of ideas.

Drawing on interviews with both cyber-skeptics and cyber-optimists, from t