Over a career that spanned nearly 60 years before he died in 2005 at age 95, Peter Drucker single-handedly invented the field of management theory. For most of the last half of the 20th century, he was the superstar CEO's go-to guru, counseling everyone from Alfred Sloan to Andy Grove. And not in the fuzzy-headed, inspirational, bromide-spouting guru sense you see today. Drucker had no time for discussing who moved your cheese, and his insights were distinctive for being simultaneously crystalline yet deeply contrarian and, frequently, a generation ahead of their time. Just one example: He was talking about the rise and importance of "knowledge workers" in the 1970s, when the phrase was a good two decades from common parlance. With 30 books to choose from, it's probably best to start with The Essential Drucker, a potent 26-piece collection selected by Drucker himself in 2001 as a comprehensive representation of his life's work.