This book is in many ways a sequel to the author's earlier The Historical Jesus. Like that work, it is a scholarly study, making use of a very large amount of material drawn from literary, anthropological, and historical sources as well as from the apocryphal and canonical gospels. The presentation and evaluation of this material make up the body of the book. This is likely to be demanding reading for those outside the field of New Testament scholarship, although I think it is on balance somewhat more approachable than the earlier book, in part because Crossan seems rather more willing here to come out openly and say what he thinks about what he has discovered.
The questions he addresses are certainly very interesting and challenging. Little is known about the earliest years of Christianity: the 30s and 40s. Once we reach the 50s we have the letters of Paul, but what was happening before that time? There are no directly relevant documents for those early years; hence Crossan's 'interdisciplinary' approach, including a consideration of the reliability of oral testimony. And some fairly revolutionary ideas emerge; revolutionary, that is, from a conventional Christian standpoint. So we need to keep in mind that Crossan is no atheist or agnostic; he is, in fact, an Irish Roman Catholic, though certainly an unusual one.
It is often said that it is Christ's resurrection that accounts for the birth and spread of Christianity across the Roman Empire, but Crossan doesn't accept this. In the early first century, visions, apparitions, and resurrections were not considered absolutely extraordinary, let alone totally unique. The ancient world was full of stories about such events, and about gods and goddesses appearing on earth in various guises and performing wonders. And although Paul laid great emphasis on the resurrection of Jesus, he didn't think of this as a unique event; on the contrary, he regarded it as a token of the forthcoming general resurrection, in which all Christians would share and be transformed.
So what is special about Jesus and his resurrection? For Crossan, what is important in the birth of Christianity (which he emphatically sees as something that happened within Judaism, not in opposition to it) is "the interaction between the historical Jesus and his first companions and the continuation of that relationship despite his execution". Note the "despite": it becomes clear in the course of the book that Crossan does not believe in a physical resurrection. He provides a detailed and critical discussion of the crucifixion and its aftermath, in which he questions most of the details of the New Testament account, including the entombment; and he regards the 'empty tomb' story as a fiction. He makes the interesting suggestion that the narrative of the resurrection was formed as a passion-resurrection story via the performance of a ritual lament by women. Here he finds an analogy with lament traditions in other societies, including Ireland and Greece.
But if there is no resurrection in the physical sense, how are we to understand it? Crossan speaks instead of the continuing incarnation of divine justice in other human beings; "the divine meaning of life is incarnated in a certain way of living". Justice is for Crossan a key concept, at the heart of religion. Whether he believes in a transcendental God from whom justice stems isn't clear to me.
Crucial to his attitude to the resurrection is a comprehensive rejection of dualism. Paul, Crossan suggests, introduced a note of Hellenistic dualism, a form of Platonism, into Christianity, so that the spirit was increasingly thought of as transcendent over the body and the flesh as irrelevant to the soul. Throughout its long history, Christianity has moved ever closer to the dualistic position. Crossan is out of sympathy with this trend. He distinguishes what he calls a sarcophilic (flesh-loving) and a sarcophobic (flesh-fearing) attitude, and identifies himself as sarcophilic. Sarcophilia is monistic, sarcophobia dualistic. The scholarly attempt to reconstruct Jesus is necessary for monistic and sarcophilic Christianity, he believes, but not for dualistic and sarcophobic Christianity. (His coining of these neologisms has led to an unfortunate proof-reading error on p. 2, where we get Monastic and Sacrophilic [sic] Christianity in place of Monistic and Sarcophilic: a transmutation which makes nonsense of his concluding punchline at the end of the prologue.)
There have been other attempts to reevaluate early Christianity radically; some authors, such as Freke and Gandy in The Jesus Mystery have even claimed that Jesus was a completely fictional character. This seems extremely improbable, but the Jesus who appears. somewhat indistinctly, from Crossan's reconstruction is more believable.