The poet, Alfred Lord Tennyson, is reputed to have called the book of Job "The greatest poem of ancient or modern times". It is, indeed, a poetic masterpiece; one of the most original poems in the history of mankind, and it is also is one of the most dramatic illustrations in the Bible of the interrelationship of God, mankind and Satan.
There is much argument as to what is the basic theme of Job. There are many opinions - the patience of a good man under testing, why do the innocent suffer? The tragedy of life in a fallen world, justification by faith, the incomprehensibility of God's dealings with man, even a parable of suffering Israel - all have been suggested.
One reason why it may be difficult to find a unifying theme is that it really happened! This is not someone's opinion about spiritual matters but an event that is reported in detail and then set in a different literary style.
Bill Cotton has put together a fascinating study of the book of Job. To aid the reader he has added highlight boxes throughout the commentary that discuss basic problems and the flow of thought.