Where does the book of Job come from?

The beginning of Job in our Bibles is identical to the Book of Jasher Chapter 22 supposedly transcribed from Greek Hebrew in the 16th century AD lost in time and then again in 1840 now published everywhere. Jasher starts off with the discourse between God and satan such as '' Have you considered my servant Abraham........then God asks satan where did you come from and satan replies '' have been going to and thro on the earth'' This is JOB the first chapter as we know it but appears in Jasher 22 as Abraham. This is where the similarity ends as Jasher then writes about Abraham sacrificing Isaac and the death of Sarah stating she died because of heartache and joy from what Abraham was doing to Isaac. Now just before this paragraph in Jasher 22 which copies our Job or Job copies Jasher but changes name to Abraham we have in Jasher a few paragraphs above a man named Aram son of Zoba son of Terah and his second wife stating Aram was very rich having 3 wives 12 children boys and 3 daughters and cattle and land, this Aram sounds to me like the Job we know...hope this helps you and others

There are 5 verses missing from the Masoretic Text that give some more background on Job:

And Job died, an old man and full of days: and it is written that he will rise again with those whom the Lord raises up. This man is described in the Syriac book as living in the land of Ausis, on the borders of Idumea and Arabia: and his name before was Jobab; and having taken an Arabian wife, he begot a son whose name was Ennon. And he himself was the son of his father Zare, one of the sons of Esau, and of his mother Bosorrha, so that he was the fifth from Abraam. And these were the kings who reigned in Edom, which country he also ruled over: first, Balac, the son of Beor, and the name of his city was Dennaba: but after Balac, Jobab, who is called Job: and after him Asom, who was governor out of the country of Thæman: and after him Adad, the son of Barad, who destroyed Madiam in the plain of Moab; and the name of his city was Gethaim. And his friends who came to him were Eliphaz, of the children of Esau, king of the Thæmanites, Baldad sovereign of the Sauchæans, Sophar king of the Minæans [Job 42:17-22 LXX].

Thus, Job was a grandson of Esau. Interestingly, although God charged Abraham to be blameless [Genesis 17:1], Job - a Gentile - is the only person in the entire Old Testament who is actually called blameless, at least in the Septuagint version.

There are suggestions that Uz is in central Syria, north of Israel, because of a genealogy in Genesis 10:23, but hard evidence for its location is not so readily available. Reference to attacks by Chaldeans (Job 1:17) would normally place the location of Uz to the east of Palestine, but reference to the Sabaeans would probably place its location in southern Arabia. One of Job's friends came from Teman in Yemen, while another was a Naamathite, from coastal Palestine, so these widely separated locations do not help. In any case, the location, or supposed location, of Uz would do little to identify where the book was actually written.

R. N. Whybray says, in 'The social world of the wisdom writers', published in The World of Ancient Israel: Sociological, Anthropological and Political Perspectives (edited by R. E. Clements), page 239, the book could not have been written without a wide knowledge of the literary world of the ancient Near East outside Palestine. This fact, together with the unexplained peculiarities of the language of the poetical part of the book, has led some scholars to suppose that the author was either a Jew living outside Palestine, or even a non-Jew.

Although some of the material in Job is undoubtedly quite ancient, from the evidence presented here, the Book of Job is post-exilic in its existing form, probably written in the fifth or fourth century BCE. This suggests the author might have been the descendant of a Jew who had remained behind in or near Babylon. Jerusalem became quite prosperous during the Persian period, so even a Jew living in Jerusalem could have gained a wide knowledge of the world outside Judah, through commerce and travel. Unfortunately, scholars have not been able to ascertain just where the book was written.