I had a casual Protestant upbringing, so I was aware that Jesus healed people and told parables and made a lot of bread and fish on one occasion (oh yeah, and he was born in a manger and crucified about three months later, every year). Beyond that, not much. So even though the author is a self-proclaimed blasphemer, it turns out I learned a lot about Jesus's life. There were a number of points where I looked up things and they were actually in the Bible, although I believe the author's recountings of Mary's alcoholism and Jesus's wrestling and whoring are apocryphal. The darn thing actually has made me want to get around to reading the official Gospels, even though I'm sure they will seem bowdlerized after this book.
The most fun part for me was the parables, which SoG's narrator freely admits to ad libbing: "Woe unto you, lawyers! Woe unto everyone, apparently! But back to the lawyers!" and trying to be deliberately obtuse: "New wine should go into new skins, and old wine into old skins. People like old wine better than new". Eventually Jesus just fobs the parable-writing onto Judas. Hijinks ensue. I won't spoil the ending.
The prose is mostly blunt and sarcastic. Arundhati Roy fans should go elsewhere.
Also, the story starts out with some Heavenly machinations and a short bio and necro of Murt, the eponymous Stuntman. This is all well and good, but it isn't really relevant once the Jesus part kicks in.