They helped invent the bar code. They revolutionized business schools and created the corporate practices that now rule our world. McKinsey employees are trusted and distrusted, loved and despised. They are doing behind-the-scenes work for the most powerful people in the world, and their ranks of alumni include the chairman of HSBC and William Hague. Renowned financial journalist Duff McDonald uncovers how these high-priced business savants have ushered in waves of structural, financial, and technological shifts but also become mired in controversy across the years.

Discover how the firm celebrated Enron's disastrous corporate structure and how they've been instrumental in the government's controversial NHS reforms. Are they worth their astronomical fees? And what do firms and governments actually get for their money?

Based on exclusive interviews with key McKinsey players and written in gripping prose, this is a revealing window onto one of the most secretive and powerful companies in the world.