When is the last time a book that was relevant to Search Engine Marketing wasn't obsolete by the time it hit the printing press? For most of us, the appeal of SEM is its dynamic nature, a constantly changing environment with a relatively level playing field. This doesn't translate well to printed materials that take time to edit, review, print, and distribute. With the immediacy of breaking news, great SEM reporting and frequent blog posts, it's no wonder our feed readers have become our primary source of knowledge and information.

An often overlooked part of SEM is the "Marketing" part. Viewed in context, marketing on search engines is relatively young, but marketing in general has been around for centuries. Many of the principles that have been proven and refined over time can be applied to SEM, but you won't read about them in your daily dose of blog posts. For this, you might have to turn to the printed medium: books. Buy them, read them, think about them, and your business will benefit.

The Search by John Battelle, 2005

A great primer on search engine history and Google's rise to the top. Battelle covers a lot of ground and puts today's engines' vast capabilities in perspective when compared to earlier versions. Along the way, he dives into advertising and marketing opportunities within them and illustrates the game-changing technologies that made it all possible. Called "The Database of Intentions," Google is covered extensively from internal and external viewpoints through detailed interviews with the most powerful forces behind its success (and potential downfall). A must-read for anybody that wants to get a full dose of Search Engines 101.

Ambient Findability by Peter Morville, 2005

Despite the esoteric title, Morville's work covers the technologies, theories, and formulas behind modern "search engines." Going beyond just Google and Yahoo!, he relates all forms of search to "the convergence of information and connectivity" and details what can only be described as "universal search" long before we heard about it from Google. My one critique would be that he seems too comfortable with the notion that we have achieved a state of "unlimited findability," but I think we all realize that today's search engines are just the tip of the iceberg. This book is not explicitly about search engine marketing, but you will learn the fundamental principles that all search engines must obey, thus making you a more informed marketer. Knowing the possibilities and limitations of search engines is key to anticipating and taking advantage of future evolutions in search.

The Long Tail by Chris Anderson, 2006

The only book on this list that can be classified as a "marketing" book, even though it deals more with commerce and culture. By now we are all familiar with "The Long Tail" theory and have used it extensively in the field of search engine marketing. However, most of our non-search savvy clients and friends have not yet grasped the concept. Imagine the knowledge you can share by being the first to turn them on to this idea. Without reading the book, you may have missed his enlightened commentary on the future of many industries, including television, manufacturing, toys, software, and yes, search. The two basic secrets are "Make everything available" and "Help me find it," but there is so much more to it than that. Search marketers will benefit from learning how to explore and exploit the "infinite aisle."

Don't Make Me Think! by Steve Krug, 2006

Perhaps the craziest book title on the list, but this easy-to-read (and funny) guide to web usability will open your eyes to the way average people "really use the web." It's easy to forget how jaded SEMs are with our power searching operators and lightning-fast consumption of content. I offer this as a book to search marketers because search engine marketing doesn't end when a visitor clicks a link to come to your site. All your efforts will be wasted and your huge traffic counts will be nothing but lost if visitors can't find their way around a site. As an SEM, spend a little time improving your site and make your traffic work harder for you. Learn how to give users what they want, increase your conversion rates, and amplify your SEM efforts by converting more visitors to sales. 

Call to Action by Bryan and Jeffrey Eisenberg, 2005

If I had my way, "Call to Action" would be renamed "Conversion University." The Eisenbergs masterfully cover complex subjects such as eye tracking, color selection, copy length, and interactivity, all with a focus on increasing conversion rates. Combining these theories with Krug's usability best practices would have a dramatic impact on nearly every company's online results. The beauty of this book is in its study of human behavior. Before reading this, I could have guessed that the color red implies "vitality, activity, desire, appetite, and craving," but I never would have guessed that yellow suggests, rather than stimulates, "a desire for change, that things are never quite at rest." Full of screenshots and diagrams, this book makes it easy to see the cause and effect of your choices when laying out a site or assisting a client with theirs. Either way, increasing conversions takes some of the pressure off of those tasked with increasing traffic at all costs.

Each of these books offers something different to a Search Engine Marketer; historical context, search theory, conversion optimization, and more. It's hard enough to find time to read all the blog posts each day, but spend some time reading these books and your business (and bottom line) will surely benefit.