This book isn't entirely wrong. It contains something thoughtful observations about how to live your life in retirement. Unfortunately, it isn't all that insightful and it's HIGHLY repetitive. This is basically a newspaper article put in book form in order to make money. I'm glad I didn't pay money for it.
A lot of his prescriptions are so obvious as to be laughable: be financially secure, be smart about your money, be active, have pursuits, have friends, travel. "Live near your kids" seemed obvious to me but seems like it might not be part of more standard advice. Don't support your grown kids, or support them less, is probably the most controversial, though I see his point.
The biggest problem with the author's approach is his blind trust in his data and his ignoring of (or ignorance of) the complications of correlation and causation. In many ways this is like the studies you see every few months showing that people who drink expensive liquor, or attend museums or the opera, or own BMWs, live longer. All of these are obviously just stand-ins for wealth. People with more money are more likely to do those things. No one can lengthen their life by upgrading the quality of their liquor or buying a sports car.
Some of the author's prescriptions make as little sense as that: having an adult kid at home for example. While I don't doubt that it's good advice to foster independence in one's children and that retirees with independent kids are generally happier, I am very doubtful that for any given couple, having a child stay home actually makes them unhappy. It's much more likely that a high proportion of stay-home kids have problems of one sort or another, which likely correlate with other problems that make people unhappy.
Also, considering that he gives financial advice, I found his advice to pay off your mortgage to be stupid being malpractice. I should pay off a 2% loan with funds that are currently returning 20% in the stock market? All because he argues that no mortgage gives "peace of mind???" This is such bad advice as to be offensive. 20% returns on my money give me "peace of mind". It's not like your house is free once it's paid off anyway; you still need to pay taxes and insurance....
The most interesting takeaway from his research was that after a certain amount, he thinks more money doesn't make people happier. I hope he's right about that!