Nothing succeeds in business books like the study of success. The current business-book boom was launched in 1982 by Tom Peters and Robert Waterman with In Search of Excellence. The trend has continued with a succession of experts and would-be experts who promise to distil the essence of excellence into three (or five or seven) simple rules.The Three Rules is a self-conscious contribution to this type of writing； it even includes a bibliography of “success studies”. Michael Raynor and Mumtaz Ahmed work for a consultancy, Deloitte, that is determined to turn itself into more of a thought-leader and less a corporate repairman. They employ all the tricks of the success books. They insist that their conclusions are “measurable and actionable”-guides to behaviour rather than analysis for its own sake. Success authors usually serve up vivid stories about how exceptional businesspeople stamped their personalities on a company or rescued it from a life-threatening crisis. Messrs Raynor and Ahmed are happier chewing the numbers： they provide detailed appendices on “calculating the elements of advantage” and “detailed analysis”.The authors spent five years studying the behaviour of their 344 “ exceptional companies” only to come up at first with nothing. Every hunch (直觉) led to a blind alley and every hypothesis to a dead end. It was only when they shifted their attention from how companies behave to how they think that they began to make sense of their voluminous material.Management is all about making difficult tradeoffs in conditions that are always uncertain and often fast-changing. But exceptional companies approach these tradeoffs with two simple rules in mind, sometimes consciously, sometimes unconsciously. First： better before cheaper. Companies are more likely to succeed in the long run if they compete on quality or performance than on price. Second： revenue before cost. Companies have more to gain in the long run from driving up revenue than by driving down costs.Most success studies suffer from two faults. There is “the halo (光环）effect”, whereby good performance leads commentators to attribute all manner of virtues to anything and everything the company does. These virtues then suddenly become vices when the company fails. Messrs Raynor and Ahmed work hard to avoid these mistakes by studying large bodies of data over several decades. But they end up embracing a different error： stating the obvious. Most businesspeople will not be surprised to learn that it is better to find a profitable niche(隙缝市场）and focus on boosting your revenues than to compete on price and cut your way to success. The difficult question is how to find that profitable niche and protect it. There, The Three Rules is less useful.