It ranks among the unquestioned laws of American big business over the last half century: If you want to be taken seriously, you hire McKinsey & Company.

FOUNDED IN 1926, McKINSEY CAN LAY CLAIM to the following partial list of accomplishments: its consultants have ushered in waves of structural, financial, and technological change to the nation's best organizations; they remapped the power structure within the White House; they even revo­lutionized business schools. In this book, star financial journalist Duff McDonald shows just how, in becoming an indispensable part of decision making at the highest levels, McKinsey has done nothing less than set the course of American capitalism.

But he also answers the question that's on the mind of anyone who has ever heard the word McKinsey: Are they worth it? After all, just as McKinsey can be shown to have helped invent most of the tools of modern management, the company was also involved with a...