I recommend: "Management: Tasks, Responsibilities, Practices" by Peter Drucker, "Positioning: The Battle for Your Mind", by Al Ries, Jack Trout and "Re-imagine!

I recommend: "Management: Tasks, Responsibilities, Practices" by Peter Drucker, "Positioning: The Battle for Your Mind", by Al Ries, Jack Trout and "Re-imagine! Business Excellence in a Disruptive Age" by Tom Peters. They aren't all strictly marketing books but they are awesome as well as informative.