This book was originally published in the 70's, and it's most recent edition published in the 90's. Despite it's age, much of the topics remain relevant today. The principles remain timeless, though the explanations can be dated.
The underlying principles of the book are still, in most cases, relevant today. However many of the examples are dated (such as references to older methodologies).
Much of the book is dedicated to getting the main point across (don't micromanage, let people do their job). This can make it feel repetitive and dull at times.
The author discusses how haste and unrealistic schedules will negatively impact a project. Causing the deadline to extend well past what it could have, had a realistic time frame been put in place initially.
This is a large book at 680 pages, so having the lessons summed up is quite beneficial. 27 "Best Practices" are discussed, including the pros and cons of them.
These examples are old enough for us to see whether a decision regarded as brilliant is still brilliant or has it started to strangle the company (Drucker himself points out some cases, like GM's reorganization being brilliant for its time, but something which needs to change for it to move ahead).
The author, Peter Drucker is sometimes referred to as "the founder of modern management".
He has 39 published books and was well known for his consulting work with management, working with large companies (such as IBM and General Motors).
What is a pro for some is a con for others. This book is a collection of posts from the author's blog, meaning there is often very little flow between the chapters.