ASKING THE IMPORTANT QUESTIONS ("NO, REALLY" EDITION): Who really wrote the Book of Job? Job, possibly the strangest book in the bible, is based on legends going back thousands of years, and is written in a very unusual form of Hebrew (Elon Gilad, Haaretz).
I think Qoheleth and Job are both in the running for the strangest book in the Hebrew Bible. Ezekiel has his moments too. But be that as it may, this article gives a good overview of the scholarly state of the question concerning the origins of the Book of Job. The only thing I would add is to mention Bruce Zuckerman's theory that the poetic dialogues in Job are a satire of the original story, which is more or less the one found in the prose prologue/epilogue. I think his theory has some explanatory value and is worth keeping in mind.