WHEN it comes to John Maynard Keynes and his economic theories, the economist has long been a lightning rod as tall as the Empire State Building. Yet examining his investment success is another matter, and far less prickly.

Although this is a largely unknown side of his life, Keynes, while scourging Wall Street and advocating public spending to create jobs, was creating several fortunes by managing money. This part of his life should be of great value to anyone interested in creating and managing wealth.

The Keynes whom history knows best was the guiding light behind the many New Deal job-creation programs and several Keynesian stimulus programs since then, including the Obama stimulus plan of 2009. He was the intellectual father of the Bretton Woods postwar economic accords. He was also a bon vivant at the heart of the quasi-bohemian Bloomsbury group, a patron of the arts and a philosopher....