McClory raises crucial questions regarding the role of the papacy in both the Catholic Communion and christendom at large. While he is sympathetic to the Catholic Church's authority structure, his reading of the history of the dogma of Papal Infallibility has lead him to understand that the doctrine has been influenced greatly by less than Christian motivations and less than Scriptural perspectives.
While many Catholics would reject his conclusions as based upon an inability to see the Holy Spirit's hand in history, or that he misreads the historical record (because we all know that God uses even wrong motivations to accomplish His will), I still think that they could find much value in this book since it will help them to understand the perspective of critics of the Church's dogmatic formation on the principle of authority.
As an Eastern Orthodox, I found it useful for the same reasons, disagreeing with the author at various times, but overall appreciative of his analysis. It is not a fluffy book that skims the surface and it is very well-written.
Going to Catholic schools for 17 years (kindergarten through grad school) we were always taught that the Pope could be infallible. I didn't understand it then, and as an adult couldn't get my mind around the concept until I read Professor McClory's book. It's a fascinating account of last minute politics, desperate pleas, and the passions of those on both sides of the issue when it was to be decided. It's not really normal for me to sit down with a book on the history of infallability in the Catholic Church and read more than a few pages at the bookstore. This one I bought, took home, and read twice. That should say something about the way Mr. McClory writes, and how what should be dry subject matter is suddenly as relevant as the changes the next Pope will bring. An excellent book.