Suggestions on books about marketing/business theory

[Agent]

I was wondering if anyone has any suggestions on books about general business/marketing theory and principles that they would like to recommend?

I don't have a formal business education but I've been self employed for a few years. It dawned on me a while back that I should read some books about marketing to help consolidate some of the information I've absorbed over the years (much of it relating to web marketing, a lot of it learned here.)

Do you guys/gals have any book recommendations that have helped you over the years become better in this business or others? Have you read any books that are not specifically business/marketing related but have given you ideas or wisdom that relate to the business? Strangely, I've found books about military history motivating. They seem to motivate me to script, design and build after reading them