Philip Kotler provides an easy-to use checklist for you to improve your marketing performance. You can print the ten items of the list on a single page it and review it regularly to find something useful. The book itself is very easy to read and is targeted for broader audience. It provides both lots of real-life examples and advices.
There is a similar book, written two years before. It is the same in usefulness, but more entertaining and vivid: "A Genie's Wisdom: A Fable of How a CEO Learned to Be a Marketing Genius" by Jack Trout. It also has has 10 chapters - in each chapter, Trout answers an important marketing question. Please consider reading both of them.
If you like to go further, I can recommend the books by Jack Welch: "Winning" and "Straight from the Gut". Although the are not explicitly about marketing, you will find a lot of marketing genius from them.
