On Labor Day I ordered, for my Kindle, Princeton New Testament scholar James Charlesworth's The HIstorical Jesus: An Essential Guide. I read half of it yesterday. It's very good, very clear. His presentation of the various "quests" for the historical Jesus was well put together. His chapter on the criteria used to determine the historical authenticity of the Jesus story was excellent. (Years ago I read Charlesworth's Jesus Within Judaism.)
Charlesworth mentions Richard Bauckham's Jesus and the Eyewitnesses, a must read for anyone seriously and in a scholarly way interested in the real Jesus. Bauckham's work has recently challenged the "status quo" of recent NT scholarship, which concludes that the Gospels are neither biographies nor based on eyewitnesses. Charlesworth writes: "In his Jesus and the Eyewitnesses (2006), [Bauckham] argues that behind Mark lies "the official tradition of the Twelve as an authoritative body of eyewitnesses" (p. 413), and that the unique features in the Gospel of John derive "from a particular circle of disciples of Jesus in which the Beloved Disciple moved" (p. 414)." (Charlesworth, p. 32)
On Mark as biography see also Ben Witherington, The Gospel of Mark: A Socio-Rhetorical Commentary. By "biography" one must mean, when it comes to Mark, "ancient biography," biography as the genre it was at the time. To say Mark is not biographical because it does not read like biographies of today is to reason anachronistically. Witherington is brilliant as he presents this.