If you expect this book to be about the loss of a family's wealth, then you should readjust your expectations before reading. This is mostly about several generations of (very intense and fascinating) family drama. There are a lot of descriptions about Gilded Age balls and Newport mansions. Only the last 30% really details their loss of wealth, and although that was partly due to family dysfunction, it sounds like changes in law and social standards also played a major part. I suspect that a lot of Gilded Age families are no longer among the super-rich of the 21st century.
Although I was disappointed that this book wasn't quite as-advertised, I'll still recommend it as a fascinating and starkly honest glimpse into a bygone era.
It also really drove home, for me, the idea that inherited wealth can be a curse as much as a blessing. Have you ever wished you'd inherited a billion dollars? Okay, great, so has everyone. Now, imagine how your family--your parents, your siblings, your children, your relatives--would treat you if you inherited 99% of the family fortune. Or if you only inherited 1% while your brother or sister got 99%. Or if your parents inherited it, but withheld it from you. Or if your child inherited it, but you did not. Now add a layer of family dysfunction--domineering mothers, megalomaniac fathers, unexpected deaths, raging alcoholism, etc.--on top of that.
It's ironic how the Vanderbilts and their contemporaries were trying *so* hard to live like the French aristocracy before the Revolution--imitating their lavish balls, their style of architecture, and struggling to get their children married to European aristocracy so they could inherit castles and titles--and yet they didn't seem to understand why aristocracy lasted for centuries. They were just imitating the superficial trappings of it. They didn't have armies or social codes of honor to back them up. They tried to fool themselves into thinking that their power was in their family name, but it was really just the wealth.