In the new book "The Firm: The Story of McKinsey and Its Secret Influence on American Business" (Simon & Schuster), award-winning financial journalist Duff McDonald provides an intimate and incisive behind-the-scenes history and analysis of this influential and enigmatic company, which helped invent what we think of as American—now global—capitalism. With unprecedented access to current and former McKinsey employees, McDonald for the first time tells the whole story of The Firm—a story that is inextricably tied to the dramatic and fluid story of American business itself in the twentieth century. The following is an excerpt from "The Firm":

Two minutes out of business school, Jamie Dimon decided to become a consultant. The experience left him unimpressed, and he has looked down on it since. "It's substitute management," he told me when I was deep into writing his biography. "A Good Housekeeping seal of approval. It's political, so if you make a decision, you can say, 'It's not my fault, it's their fault.' ... I think consultants can become a disease for corporations." Dimon, who went on to become the chairman and CEO of JPMorgan Chase and was hailed as an Olympian financier for steering the bank above Wall Street's 2008 humbling—only to be somewhat humbled himself four years later when its own trading caused more than $5 billion in losses—made one exception to his consultant rule. Most consulting engagements weren't worth the price paid, he said, but McKinsey—well, it was the real thing.