First, I had a few issues with the author's frequent use of Scripture. Not so much the fact that he used Scripture, of course! Rather, the way he used it left much to be desired, often using short "proof-texts" that didn't really support his arguments that well. Here's an excerpt that illustrates this tendency, referring to the context of Jews having multiple wives:
It was this polygynous culture that Jesus entered. But he never lent any support to polygyny. Whenever he spoke about marriage or used a marriage illustration, it was always in the context of monogamy. He said, "The two [not three or four] will become one flesh" (Matthew 19:5). Another time he said that if anyone wished to follow him, he would have to choose him over his brothers, sisters, mother, and his wife (Luke 14:26). He did not say "wives."
His overall point is a good one, but the casual Scripture-dropping seems out of place.
At other times, the author inserted too much extraneous editorial comment. In discussing the impact of Christianity on the arts, Schmidt writes the following about Michelangelo:
His last work, The Last Judgment, shows God as a stern judge, surrounded by the apostles, who look questionably at his acts of condemnation as demons carry away the condemned. Great as this work is, it overlooks the Christian gospel, namely, that there is also forgiveness for those who by faith in Christ "repent, and believe in the good news" (Mark 1:15 NRSV). This shortcoming of The Last Judgment is also true of some other Christian art produced during the late Middle Ages as well as during the earlier years of the Renaissance, whose many biblical teachings are often portrayed in the context of God's condemning law.
Personally, I find these comments pretty non-sensical and carrying a typical modern Evangelical tendency to blunt the force of Scripture's "hard teachings." Also, notice the throwaway use of a prooftext.
But these detractions aside, the book is a marvelous wealth of historical data on the impact of Christianity. The chapter on the sanctity of human life is great, detailing the gradual victory of Christian morality over the dominant Greco-Roman practices of abortion, infanticide, gladiatorial combat, etc. There are also chapters on Christianity's impact on sexual morality, compassion for the sick and poor, and education. I thought the chapters on Christianity's influence on politics and the sciences were pretty interesting, too, although several of the figures mentioned have had their Christianity called into question (Newton, Jefferson, etc). All in all, this is definitely a good source of support for the postmillenial hope that Christ will greatly expand His kingdom, far beyond the mere saving of souls, actually transforming the whole world.