To quote from their introduction
This guide is designed to describe all major aspects of SEO, from finding the terms and phrases (keywords) that can generate qualified traffic to your website, to making your site friendly to search engines, to building links and marketing the unique value of your site.
The world of SEO is complex and ever-changing, but you can easily understand the basics, and even a small amount of knowledge can make a big difference. Free SEO education is also widely available on the web, including in guides like this! (Woohoo!)
"If you're serious about improving search traffic and are unfamiliar with SEO, we recommend reading this guide front-to-back. We've tried to make it as concise and easy to understand as possible, and learning the basics of SEO is a vital first step in achieving your online business goals.
Go through at the pace that suits you best, and be sure to take note of the dozens of resources we link to throughout the chapters — they're also worthy of your attention."