I just finished reading Richard Bauckham’s Jesus and the Eyewitnesses: The Gospels as Eyewitness Testimony (Eerdmeans, 2006). It was quite an encyclopedic treatment of the subject. Written to appeal to readers coming from a higher critical standpoint, it came to rather conservative conclusions that the Gospels, particularly John and Mark, portray themselves as constituting eyewitness testimony, not the sort of community-evolved tradition/legends that form critics have long claimed.
Still the work is not without its weak points. Bauckham’s reading of Papias on “John the elder” (i.e. not the son of Zebedee) requires a highly interpolated translation, and requires one place the otherwise unknown John at the last supper, where the Synoptic Gospels have room only for the 12.
Bauckham also follows the mainstream Markan priority approach such that in the end the 3 Synoptics are but one witness to most of the events they have in common. The problems with that approach are too complex to deal with here. Perhaps it will suffice for the moment to note that the Fathers testify (at least two totally independent lines) that the Greek Matthew was based upon an Aramaic (‘Hebrew’) predecessor, not upon Mark. The mainstream allows human speculation to trump corroborated historical data–only in Gospel criticism!