This book was a bit of a stretch for me, but I do have an interest in "the historical Jesus," the history of the Christian churches, etc.
Wilson seems to be convinced that Jesus, according to all the evidence we had, had no thought of founding a church, or even necessarily offering a teaching to Gentiles. He may not have thought of himself as "the Messiah." He clearly wished to bring a kind of reform to Judaism, and it was clearly along the lines of "don't think that by living righteously, i.e. according to the rules, you are doing all that is needed to please God. What is needed is a kind of brutal truth about oneself, an intense emotional commitment--which may be just as likely from a suddenly reformed sinner as from a righteous person. This kind of thing will always anger at least some of the conventionally righteous people, and inspire some of the idealistic young.
Wilson doubts that the Pharisees were monolithically opposed to Jesus, and he suggests that all the indications to the effect that the Pharisees or other official Jews insisted on giving Jesus up to the Romans, while the Romans themselves were less zealous about persecuting him, are later additions designed to help make peace between Gentile Christians and the Roman Empire. Wilson does a nice job of conveying a world in which Jerusalem was a splendid city, with a splendid temple (destroyed a few decades after Jesus' death--in deliberately reaching out to Gentiles, the church-builders were trying to build on a winner rather than a loser). There were various Jewish sects, many not that different from what is known as the early, strictly Jewish Jesus-sect. (The disciples were members of various groups, some of them practically terrorists). There were certainly many healers and prophets, and even the Gospels include accounts of people other than Jesus who come back from the dead--not all of them brought back by Jesus himself. The notion that Jesus, and only Jesus, can bring you back from the dead if you repent your sins, and that a new church (with new Pharisee-like rules) is the best mechanism to achieve this result for a lot of people, all seems to be added later.
As Wilson says, the notion that the unrighteous have as much chance of salvation as the righteous, so long as they have the appropriate experience at a crucial moment, is in opposition to almost any system of ethics--any belief that virtue is desirable for itself, or is noble. In the Jesus view (Publican vs. Pharisee, prodigal son, etc.), virtue is only desirable if it achieves the same result that vicious people might achieve by a more direct emotional path. Perhaps being in the habit of repenting your sins helps prepare you for death, and the big repentance that really counts; but then again, maybe not.
The stories of the birth of Jesus are almost certainly later additions, designed to show that his spectacular adulthood and death were hardly anticipated, even by close observers, at the time of his humble--even squalid or humiliating--birth. The death stories seem to have more details that sound like they come from eye witnesses. Jesus tells the disciples they are all going to Jerusalem, that there is a man who has a donkey for Jesus to ride on, and that another man will offer a room--in a Jerusalem that is already crowded for Passover--for a Passover meal. Had Jesus made all these arrangements? Did he expect to be executed, and then expect that the world would end about five minutes later?
Paul may have concealed the extent to which he was a persecuting Pharisee, who struggled with Jesus' radical teaching, then turned it against the Pharisees in particular. He as much as anyone invented the notion of a Gentile Christian church, with specific rituals including the Eucharist (which Wilson says Jesus did not found).