Canon of the New Testament

Since I'm not taking any classes during the summer, I've had a little more time to read books that have been on my reading list. Currently, I'm half-way through reading Bruce M. Metzger's The Canon of the New Testament: Its Origin, Development, and Significance. In this book Metzger discusses the historical development of the New Testament documents and the way that they came to be recognized as canonical. According to Metzger the canonization of the New Testament was not a quick process in which church councils arbitrarily picked certain books to be part of the canon; rather, the process was long and gradual. Metzger maintains that external pressures such as persecution and heretical teachings (by men such as Marcion, who rejected the Old Testament and much of the New Testament) pushed the church to recognize which documents were authoritative and which ones were not.