I read this a while back, the audiobook version actually. The book centers squarely on Cornelius Vanderbilt, the Commodore, who built the shipping and railroad empire from nothing. He's the absolute engine of the 'rise' part. The narrative then shifts heavily to his descendants, especially his grandson, also named Cornelius Vanderbilt II, who built The Breakers in Newport, and his wife, Alva Vanderbilt. She's a force—pushing their way into New York society, marrying their daughter Consuelo off to a British duke. That marriage is a huge, sad chunk of the 'fall' narrative, showcasing how the family's wealth became a gilded cage.
The other key figure is the author's own connection, Anderson Cooper. His mother was Gloria Vanderbilt, so he's writing about his own family's dissipation of that colossal fortune. He frames the whole story through that lens, which gives the historical account a very personal, almost melancholy tone. It’s less about dry business and more about the corrosive effect of that much money across generations.