The story is widely known and is probably the most often told story (be it fictional or historical) on Earth. Here it is told from the perspective of Jesus himself. That sounds very promising, I think. Mailer's objective was to "humanise" Christ, to make him more understandable as (also) a human being. I do not think Mailer succeeded.
It is really amazing how close Mailer sticks to the original, i e the gospels. Of course he can't be blamed for that; it is quite a step to try to rewrite them. But since that is what Mailer obiously has tried to do, I think he should have had more courage and try some alternative explanations to, for instance, the miracles. I know this would upset quite a lot of people, but if the aim is to present Jesus more as a human being I find the miracles a little out of place.
Moreover, I find the (human) Jesus Mailer portraits a rather unpleasant person; instead of being righteous he appears self-righteous, instead of being humble, pompous.
Of course you can try to read the book as a "normal" novel, but I think the story is too well-known for that. If you know from the very beginning what will happen next, then the only reason for reading on is the beauty of the language. Granted, the language can be beautiful in places, but then again, it is not Mailer's own, but a very biblical kind of prose.
I'd stick to the original, this book has not much to add. For more convincing "biblical" novels I recommend the Swedish author Marianne Fredriksson, many of whose books have been translated into English.