David Cannadine's very detailed biography of Andrew Mellon weighs in at over 620 pages (with another 150 pages devoted to footnotes and an detailed index). Although it was far from being a light read it was interesting and enthralling for two reasons.
The first is that Cannadine succeeds in portraying Andrew Mellon in a balanced way - conveying a sense of what he was like (good and bad) both as an individual and as a financier, business man, art collector, public official and philanthropist.
The second is the way in which Mellon's life was a reflection of the various "ages"that he lived in. He was a contemporary of people such as Ford, Rockefeller, Frick, Carnegie, Morgan and Gould. Unlike most of the other leading plutocrats of America's guilded age he lived long enough and remained active either in business or in public life to see both the end of "his"era but also the backlash during the Great Depression and the Roosevelt presidency. Cannadine conveys an excellent understanding of the issues and realities of life during the guilded age in particular and the spectacular gulf between the ultra rich and the ultra poor. In many respects the book can be viewed as work of economic and social history as much as a biography.
An excellent read.