The 22 Immutable Laws of Marketing is a valuable read from the great minds of Al Ries and Jack Trout. It focuses on marketing strategy, especially branding. It is geared towards corporate strategy so the ideas are difficult to apply to smaller businesses, but it's still very insightful marketing.
The 5 Best Points......
5. Find a category that you can be a first mover, no one remembers the second person to fly across the Atlantic Ocean (Bert Hinkler).
4. If you don't get in the mind of the consumer, it does no good to be the first mover. i.e. Altair 8800 the first personal computer.
3. Refrain from extending your brand to unrelated products. i.e. Domino's frozen pizza.
2. There is no such thing as the best product, only what is perceived to be the best.
1. If you try to stand for everything, you will stand for nothing.