By Harry S. Dent Jr.

The Great Depression Ahead: How to Prosper in the Crash Following the Greatest Boom in History

(Free Press — $27)

Dent's thing is demographics, and his previous books have aimed at revealing how changes in the U.S. population made a "great boom" inevitable. But those days are gone, he now says: Suddenly, the optimist is a doomsayer. The Roaring 2000s, as he titled a 1998 book, are at an end.