The book of Job is wisdom literature, like Psalms, Proverbs, Ecclesiastes, and Song of Songs.
What can we add to what has already been written on the Book of Job?
Is it the oldest book in the canon as its historical milieu would place it, or was it written (down) much later?
Is it merely a literary story meant to illuminate the relation between God and man-in-the-created-order, or is it historical?
We are not so foolish as to claim that we know any of these answers, or how God has in fact put His word together, but we have learned not to put the plausible stories of man in the place of what He says in His word. We will never go far wrong if we simply trust what God says, being careful readers of scripture.
What we do know is that Job is a masterpiece of literature by any metric, and one of (if not) THE greatest works of wisdom literature ever crafted. I cannot help but end with a quote from another such brilliant work:
All this I have tested by wisdom. I said, “I will be wise,” but it was far from me. That which has been is far off, and deep, very deep; who can find it out?
I turned my heart to know and to search out and to seek wisdom and the scheme of things, and to know the wickedness of folly and the foolishness that is madness.... Behold, this is what I found, says the Preacher, while adding one thing to another to find the scheme of things — which my soul has sought repeatedly, but I have not found.... See, this alone I found, that God made man upright, but they have sought out many schemes. (ESV)
The Preacher sought to find words of delight, and uprightly he wrote words of truth.
The words of the wise are like goads, and like nails firmly fixed are the collected sayings; they are given by one Shepherd. My son, beware of anything beyond these. Of making many books there is no end, and much study is a weariness of the flesh.
The end of the matter; all has been heard. Fear God and keep his commandments, for this is the whole duty of man. (ESV)