Harry Dent's theory is that the state of the economy depends primarily on what the baby boomers are up to.
If they are in a stage of life when they are buying houses, raising kids, and spending a lot of money, the economy is going to be great. As they are getting older and nearing or at retirement, they're going to stop spending, start paying off debt, and save as much as they can. That time is now, and therefore the economy is going to be very slow for the next ten or twelve years, no matter how much the government stimulates it.
This book rehashes a lot of what he already said in some of his other books. Probably worth reading, but time will tell if his predictions pan out.