Timothy Geithner,

Crown, 580 pages, $35.

The financial crisis that began with the collapse of the U.S. mortgage market was just one of many episodes of recent financial mayhem, from the Mexican and Asian financial crises of the 1990s to the euro crisis and America's near-default in the summer of 2011.

To draw common lessons from such disparate events, it helps to have had a hand in responding to them. Tim Geithner, President Obama's former treasury secretary, has certainly done so, and it shows in his book, "Stress Test: Reflections on Financial Crises."

Geithner became a point man for Robert Rubin and Larry Summers during the Mexican and Asian financial crises in the 1990s, and, as president of the Federal Reserve Bank of New York and then treasury secretary until last year, he was a central player in America's own crises. He was known for his brutal candor, and as an author, he does not disappoint. At one meeting he realized that John Thain, Merrill Lynch's chief, did not know the name of his chief risk officer, who was sitting next to him. It was, Geithner writes, "an awkward moment," and explained the sorry state of Merrill's risk management.

Geithner has been criticized for doing too little to rein in big banks before the crisis, and for doing them too many favors afterward. He concedes the first point, a bit, but on the second he is defiant. Saving the financial system was essential to saving the economy, and his book is full of charts and notes to try to prove this point.

Geithner will not convince his most strident critics, but less obdurate readers will value his advice. Governments should not respond to every financial failure, he writes, but must be ready to intervene with overwhelming force to prevent a systemic crisis.

In 2008 he had the right instinct. But taken too far, it affirms suspicions that many firms and markets are "too big to fail." Geithner thinks the reforms he helped design will enable his successors to shut down big firms without the chaos of Lehman's collapse. Only the next crisis will prove whether he is right.

THE ECONOMIST