The Effective Executive by Peter Drucker

The classic book on being a more effective executive by focusing on the things that matter. One note: you'll need to overlook the obvious sexist references to managers as "he", given that this book was written over a half-century ago. But the advice is sound and timeless for managers from any background.

From Amazon:
The measure of the executive, Peter Drucker reminds us, is the ability to "get the right things done." This usually involves doing what other people have overlooked as well as avoiding what is unproductive. Intelligence, imagination, and knowledge may all be wasted in an executive job without the acquired habits of mind that mold them into results.
Drucker identifies five practices essential to business effectiveness that can, and must, be learned:

• Management of time
• Choosing what to contribute to the practical organization
• Knowing where and how to mobilize strength for best effect
• Setting up the right priorities
• And Knitting all of them together with effective decision making

Ranging widely through the annals of business and government, Peter Drucker demonstrates the distinctive skill of the executive and offers fresh insights into old and seemingly obvious business situations.