Harvard Business Review writes about this article from their collection, "No management thinker was as prolific or as profound as Peter Drucker. Here is some of the savviest advice he offered executives." This from Harvard Business School Press! Who is better qualified to make this judgment than them?
The brief introduction describes how Drucker evolved into what he became. This article then summarizes his previous summaries of his greatest work. Eight articles are included in brief: "The Theory of the Business", "What Business Can Learn from Nonprofits", "The New Society of Organizations", "The Information Executives Truly Need", "Managing Oneself", "They're Not Employees - They're People", and "What Makes the Effective Executive".
Simply Magazine has produced most of these articles in their unabridged form for those who would later like to read the complete articles. This is an excellent sampling with the core information provided.