The book of Job chronicles the title character, Job, and his miserable suffering: he lost everything but life itself. There are not too many people that can claim his experience.
As Job suffers, God reveals himself to Job. As in each book of the Bible, the book of Job is ultimately a revelation of God himself—who he is and what he does. In other words, the book of Job is ultimately about God—the God a sufferer needs.
In particular, the God that is revealed in the book of Job is the God of all power (or sovereignty), the God of infinite wisdom, the God of absolute justice, and the God of perfect goodness—exactly what sufferers need. When we suffer, we need God to be all four characteristics.
If God is wise, just, and good, but not powerful (or sovereign), he could not execute on his wisdom, justice, and goodness. This means that your suffering would be out of control, random, or left to fate. But since God is all powerful (or sovereign), your suffering is not random or outside his control. God ultimately orchestrates all the suffering in your life (cf. Job 42:2).
If God is powerful, just, and good, but not wise, he could not accomplish the infinite ends for which he brought on your suffering. This means that your suffering would be meaninglessness and purposelessness. But since God is infinitely wise, your suffering brings about all his plans for you and the world (cf. Job 28:28).
If God is powerful, wise, and good, but not just, he could not be considered just in bringing the suffering into your life. This means that your suffering would be unfair. But since God is absolutely just, your suffering is righteous and fair (cf. Job 34:12).
If God is powerful, wise, and just, but not good, he would be cruel and vindictive. This means your suffering would be a form of punishment or revenge. But since God is perfectly good, your suffering is his loving care for your redemption (cf. Job 38:25-27, 39-41; Romans 8:28).
The sufferer needs God to be powerful, wise, just, and good. The book of Job wonderfully reveals that God is all four for sufferers like us!
For more on who God is and what he does in the book of Job, listen to the sermon series here, or pick up a free copy of the sermons put in book form at Grace Community Bible Church.