Lazard has always believed itself to be special. Its bankers have long been proud of its rise from a New Orleans dry goods store to an elite global confederacy whose riches and sophistication make them the peers of the chief executives they advise.

But, some argue, something was lost in translation when Lazard went public two years ago. So believes former associate William Cohan, author of The Last Tycoons: The Secret History of Lazard Frères, a 742-page epic that is published this month.