Being actively involved in many SEM/SEO forums, I see all kinds of questions, from very basic to very advanced. Often, if people really want to learn about a subject, a book can be a great place to start. I have read and reviewed many SEO/SEM books over the years. This past month, I have received four new books that people would like me to review, and I assume, blog about. So what do I recommend?
If you are starting out with SEO and you are clueless about the basics, I strongly recommend you buy and read Search Engine Visibility by Shari Thurow. It is an outstanding book for beginners, it lays down pretty much all the basics and explains the core principle concepts of search engine optimization in a manner where virtually anyone can understand. Shari Thurow is one of the most well known SEOs out there, she has been on the Search Engine Strategies conference ticket since its inception (I believe). Of course she is a "white hat" and some would disagree with aspect of the book. However, I still strongly feel everyone serious about getting into the SEO industry, should read this book.
After you finish that book, you are not done. Dan Thies has just released a new book with SitePoint named the Search Engine Marketing Kit. I strongly recommend you read this book as soon as you finish Shari Thurow's book. This book gets deeper into the aspects of SEO and PPC, allowing you to take the core principles you learned from Shari's book and apply them in expert fashion on your site. I have read the bulk of the Search Engine Marketing Kit (skipped over the resources section) and I can honestly say that Dan Thies is way more then a keyword research expert. He not only goes over intermediate SEO tactics, he also discusses the PPC aspect of SEM. But even more so, he has a whole chapter on "Running a Search Engine Marketing Business." This kit also has a detailed CD with Sample SEM Proposal, Client Assessment Form, Keyword Analysis Worksheet, Directory Planning Worksheet, Sample SEO Presentation, Process Flowchart, Sample SEM Services Agreement, and Site Review Checklist. The book has immense value and can easily make you a qualified search engine marketing professional.
Finally, if you really want to get advanced and learn how the search engine work, then you need to talk to the person who talks to the people. That is right, you need to get Mike Grehan's Search Engine Marketing Book. It explains how the search engine algorithms work, why they do what they do, and has exclusive, and priceless interviews with search engine representatives. Also, if you buy the book, you get a free upgrade to the 3rd edition, which is due out some time soon.
There are many other valuable SEO/SEM books out there, and I apologize if I did not include yours. I can not possibly list them all. But do a search in Google for seo book or SEM book and you should fine a nice collection. It is my feeling that those three books, read in that order will give you the knowledge you need to become an SEO Professional. The rest is up to how you practice SEM, but at least those books will give you your best shot.
For other thoughts on this topic, visit the High Rankings Forum thread named SEO Books For Starting A Career In This Field, Which are the best ones?.