Lord Acton's statement that "power tends to corrupt, and absolute power corrupts absolutely" is probably better known than he is. In this well-researched and coherently written biography, Hill, a retired journalist who has long studied Acton's work, draws on known publications as well as Acton's private notes. A highly respected historian and teacher, Acton (1834-1902) studied and maintained friendships in Italy and Germany besides England. His "compulsive note-taking" was in three languages, and the notes were dispersed in libraries throughout Europe. They were very fragmented, and Acton's granddaughter helped with their contextual reconstruction. Acton wrote almost 20 monographs in English, Italian, and German and was criticized for not further sharing his breadth of learning through writing. A devout Catholic, he edited the Catholic journal Rambler, earning it a reputation for independent intellectual thought; Acton himself disagreed with some Catholic tenets, including papal infallibility. Hill's book should be added to academic collections, though public libraries may wish to defer to the local college collections.