Perhaps I am too literal-minded, but when I pick up a book titled The One Thing You Need To Know, I assume that there will be a singular recommendation. Yet, when you reach that chapter of the book titled "Conclusion" (p. 281), Marcus Buckingham (co-author of First, Break All the Rules and Now, Discover Your Strengths) references the book by the late Douglas Adams The Hitchhiker’s Guide to the Galaxy (now a somewhat major motion picture), wherein the answer to Everything is "42." (No one is sure what the question is.) I feel rather, ah, 42 about this book. For example, right off the bat there are two things, not one. Managing and leading. Then there are three criteria used to determine the One Thing. Buckingham also lists five fears, five needs, and one focus. Three levers. It all begins to seem like Fermat’s enigma.
To get to the point of the "One Thing," there are actually two. "The One Thing all great managers know about great managing is this: Discover What Is Unique About Each Person and Capitalize on It." And, "So, while great managers discover what is unique about each person and capitalize on it, great leaders do the inverse. The One Thing every great leader knows he must do is: Discover What Is Universal and Capitalize on It."
None of this is very fresh, although Buckingham provides examples galore. Presumably, a book that was truly about One Thing would be significantly less numeric. And shorter.—GSV