The Story of the Bible, by Frederic G. Kenyon

http://www.bible-researcher.com/kenyon/sotb3.html

If therefore we look back over the earliest generations of
Christianity, from the time of our Lord to the date (somewhere about
A.D. 325) when Christianity became the accepted religion of the Roman
Empire, we see first of all a period of some forty years when the
narrative of our Lord's life and teaching circulated orally, in the
preaching of His disciples, or in written records which have not come
down to us; and when St. Paul was writing his letters to various
Christian churches which he and his companions had founded. Then,
about the years 65 to 75, we have the composition of what are known as
the three Synoptic Gospels, Mark, Luke and Matthew, Mark's being the
earliest, and Matthew and Luke using him and also other narratives and
collections of sayings. The Book of Acts belongs to the same period,
being the second part of Luke's history. Revelation is now generally
assigned to the time of the persecution of Domitian, about A.D. 95;
and St. John's Gospel also must be late in the century. Then we have a
period of rather over two hundred years, when the various books
circulated, either singly in separate papyrus rolls or combined into
small groups in papyrus codi
---SPSmith