This book traces the changeover in Christianity from the first century into the fourth, as it moved from being chiefly a Jewish sect to being a new version of Greco-Roman religion, adopting many beliefs and practices from the latter along the way. There wasn't much new here to me, but Petty writes in a very simple manner that would make for easy reading and understanding among the most general of readers looking for an introduction (I wish I'd come across the book ten years ago, when I first started heavily reading in the subject). The period covered is a very long one, including not just the first four centuries of the Christian era but also the basics of Greek philosophy and the Jewish faith going back to their founding (and constituting almost half the book). As such, one can glean a clear sense of where Christianity comes in, but the history of the four centuries that are the book's focus is even more compacted as a result. The Bible is used heavily as a source, as are Bible helps; other sources include various classics on classical, Jewish, and Christian history, and there is a general smattering of quotes from various primary sources outside scripture. The most cogent argument Petty makes comes near the end of the book, when he notes how Paul could not be the source of so many of the changes to the faith established by Jesus and the original twelve apostles, but rather such changes were really the influence of later incorporation into classical Greek thinking. The argument is laid out succinctly and clearly, as with so much of the rest of the book; however, such would be unlikely to satisfy most diehard critics, who have laid out whole books on small aspects of the subject (usually, showing just the opposite of what Petty does but in more recent times increasingly appreciating Paul in his Jewish setting and beginning to understand that he was not the antinomian or anti-Petrine figure many earlier scholars have made him out to be).