I picked this up at the library the other day, and it has been a very interesting read. I had heard awful things about it, and in fact someone had even penned a warning in the front of the library's copy that it was unorthodox and should "be read with caution." I found it to be quite different from what I had expected. The larger part of the book is a history of the papacy -- although it must be admitted that it tends to highlight the negatives. This is not meant to be a comprehensive history but a showing of evidence that at times the papacy has erred, and erred greatly. He doesn't deny the importance of the papacy or even papal infallibility, although I thought it was interesting when he gave a quote from Cardinal Newman that agreed with what I've thought, that the doctrine of papal infallibility as declared actually limits papal power rather than expanding it.
I disagree strongly with his characterization of Ratzinger's teaching, I don't think it is accurate at all, but I do think his central thesis, which he largely borrowed from Newman, is true -- that theologians, the laity and the papacy/hierarchy counterbalance each other to keep the Church on track. The chapter "The Pope's Loyal Opposition" is priceless.