Just finished this and it was phenomenal. Its the best biography that ive read so far. I dont think there is one weak point. Even his early life was fascinating thanks to his father and family dynamic and how John D reacted to it. Learning about how Standard Oil started and eventually dominated the oil industry and all of the criticisms, legal issues, and lawsuits.
I also really enjoyed reading about his philanthropy, how his conceptions changed and what each philanthropic endeavor was and did, and how people reacted to it. I mean, I really had no idea that Rockefeller had a significant part in modernizing medicine in the United States and significantly undermining the quack doctors that prevaded the medical field at the time (even though he liked the quack doctors).
Besides because being involved in such interesting events, Rockefeller is a fascinating character. He was driven, ruthless and a managerial genius when it came to making money, but completely rationalized that (and blotted out the bad stuff he did) as a sign that he was blessed by God and ordained to give away his money wisely for the benefit of mankind. Lot more to it to that obviously, but thats the basic gist of his personality.