The Book of Job presents a moral seriousness that Harvey probably found lacking in Effie. "The only problem" of the title is the problem of suffering, that is, why a loving God would allow suffering to happen. It is the only problem that matters. Job is a strange book, and Harvey explains that God comes off very badly:
'...Thunder and bluster and I'm Me, who are you? Putting on an act. Behold now Leviathan. Behold now Behemoth. Ha, ha among the trumpets. Where wast thou when I laid the foundations of the earth? And Job, insincerely and wrongly, says, "I am vile."'
But Harvey is not permitted the peace he needs to finish his book. At first, he is merely subjected to a series of visitors--most of whom are eager enough to discuss Job with Harvey, so that Spark might have a mouthpiece for her own ideas--but suddenly he is mobbed by the French police, who suspect that Effie has been working with a group of domestic terrorists that may be financed by Harvey's wealth.
What are we to make of all this? Clearly we are expected to ask to what extent Harvey himself inhabits the role of Job, which he first forswears but later seems to take upon himself. Certainly the policemen who interrogate him are like Job's comforters, who insist that Job must be at fault for his suffering, but as Harvey's lawyer notes, he doesn't suffer much. Certainly he doesn't suffer like the family of the policeman who is killed by Effie's terrorist cell, and even less does he suffer like Job. But perhaps this is a question with no meaningful answer. After all, Job epitomizes suffering, and there is no story to match his. Either we are all Job because it is the human lot to suffer, and Harvey too, or none of us are because Job's suffering transcends all others.
In his biography of Spark, Martin Stannard tells us that this inscrutable book really is about inscrutability. Spark's own opinion was that our need to understand God's motivation is a fallacy because God cannot be anthropomorphized; he is not a man. As Effie is the cause of Harvey's suffering she is a God-figure, and it is telling when Harvey admits that, in spite of all, he still loves her, though he can never understand her. Perhaps his love is even inextricable from his suffering at her hands.
Spark, as she always does, treats all of this as a brusque farce, and The Book of Job sits at the middle of it, its tragedy starker still by comparison, weighing the story down like a stone. Our own suffering is indicted too, and we are made to be slightly embarrassed when we realize how much more like Harvey we are than Job. It is like Spark to find the notes of farce that tragedy leaves in its wake, and one of her favorite details to repeat here is that after his ordeal Job named one of his new daughters Keren-happuch, meaning "Box of Eye-Paint."
Job was a life-long obsession for Spark, who had written a response to Jung's analysis of it, and most of the ideas about Job expressed here are taken wholesale from that response. There is an added element, a painting by Georges de la Tour called Job visite par sa femme that is what draws Harvey to Epinal:
Job's wife, tall, sweet-faced, with the intimation of a beautiful body inside the large tent-like case of her firm clothes, bending, long-necked, solicitous over Job. In her hand is a lighted candle. It is night, it is winter. Job's wife wears a glorious red tunic over her dress. Job sits on a plain cube-shaped block. He might be in front of a fire, for the light of the candle alone cannot explain the amount of light that is cast on the two figures. Job is naked except for a loin-cloth. He clasps his hands above his knees. His body seems to shrink, but it is the shrunkenness of pathos rather than want. Beside him is the piece of pottery that he has taken to scrape his wounds. His beard is thick. He is not an old man. Both are in their early prime, a couple in their thirties. (Indeed, their recently-dead children were not yet married.) His face looks up at this wife, sensitive, imploring some favour, urging some cause. What is his wife trying to tell him as she bends her sweet face towards him? What does he beg, this stricken man, so serene in his faith, so accomplished in argument?
We know from Job that the words his wife utters are "Curse God, and die." In her face Harvey sees his own wife. The painting provides no answers to the problem Harvey toils over, but it deepens his understanding by showing his life in Job's. Art is a way of coming to terms with the divine. So Spark too, once having toiled like Harvey over her response to Jung, has recast those thoughts in art that they might illuminate a little more of our human darkness.