Published in 1982 and showing it's age a bit now (2011), he probably intended it as a scholarly investigation of the nature of belief and religion. Unfortunately I couldn't warm to his characters although I stuck with them long enough to find out what happens in the end. It's a story in which love, joy, peace, beauty, faithfulness are all missing, full of characters who are drugging themselves because they recognise their own empty lives but seem unable to reach out and do anything about it. He trots through the arguments for and against belief through the mouth of the totally unsympathetic Timothy Archer. At one level it's an outright attack on the identity of Christ and the veracity of the Gospel accounts. On the other hand, the story lays bare the sham of dressing up selfishness, lust and greed in religious clothing and then blaming God for the results. In the end he seems to prefer the self-improvement of Buddhism but even that is unclear and it leaves a kind of helpless nhilism devoid of hope.
Read it as a curiosity from a particular place and time. No philosophy here, just emptiness.