Aquinas sees the Book of Job as a disputation on providence among friends. He suggests Job was probably a historical character but this doesn't matter so much, as the intent lies in the argument(ation): as important as what is said is how it's said: the dynamic of the exchanges between Job and his friends. As Aquinas sees it (reading from 19:25-27 that Job knows his redeemer lives), Job knows of the afterlife. His friends don't. For this reason, they are forced - by their own best intentions - to false conclusions about Job's innocence and also about providence. If another life in which just men are rewarded and evil men are punished ... is not posited, no reason can be given for the trial of just men, who, it is certain, are sometimes troubled in this world. (trans. Anthony Damico [Atlanta, GA: Scholars Press, 1989],194; on Job 10:22)
Job is trying to show them the error of their ways, but since what they don't know is so huge and transformative a thing, he's taking it slow: first showing contradictions in their views in his responses to them (a sort of immanent criticism), rather than springing the truth of immortality on them without preparation. Only in chapter 19 - and signaled by his wish that his words, unlike those which came before, be recorded permanently and for posterity - does he introduce this saving difference. (They don't get it. Perhaps because of the pain shortening his patience, his pedagogical and rhetorical efforts fall short: he causes affront in his friends rather than illumination - until backed up by the intervention of Authority.)
I've been impressed in the past by the centrality of friendship to Aquinas' account of the relationship of Job, Eliphaz, Bildad and Zophar (very unlike modern readings which see them as hypocrites, false in their friendship as well as their piety). The dynamics of disputation among friends are crucial to Aquinas' argument, which isn't just about the answer to questions about providence, but how to address them, how to discuss them, how to avoid error in them, how to guide - or learn from - your friends in them. But I had not noticed that Aquinas' first reference to friendship comes in referring to Job as a friend of God: Now it is the mark of friends to want and to reject the same things. Hence, if it proceeds from divine good pleasure that someone be despoiled of his temporal goods, if he loves God he ought to conform his own will to the divine will, so that considering this he should not be engrossed by sadness. (89; on Job 1:21)
Picture source.