Maimonides, a famous Medieval Jewish scholar, thought a lot about the Book of Job. In his opinion, Job's suffering was caused by the fact that he misunderstood his situation. Forget the death of his family or the physical torment of head-to-toe blisters—Job suffers because he's confused (source).
In this story, Job loses almost everything and everyone he loves. So it's no wonder that the book has been a source for Jewish mourning ritual. What does Job do when his family dies? He tears his clothes (1:20). And guess what? That's still a common custom today
But wait, there's more. Did you notice that when Job's friends come by to hang out with him, they don't say anything? Well, Jewish people have taken a cue from this, too: it's tradition not to speak to a mourner until spoken to (source).
Other Jewish thinkers have worked on accounting for Job's punishment, with one story positing that Job had a hand in the Exile from Egypt (source). Why would scholars speculate about this? Well, because they're trying to answer the same question that Job was. It's hard for people to accept that good people sometimes get punished for no reason; invent a reason, and the problem solves itself.
One thing's for sure. No one agrees on what the Book of Job really means. Take a look at some other viewpoints and then decide for yourself.
Job does a lot of complaining in the Book of Job. It's hard to keep track of what he's lamenting at any given moment, but at least a couple times, he wishes for a mediator who could make communication between himself and God easier: "There is no umpire between us, who might lay his hand on us both" (9:33). He's sure that this mediator would redeem him and pronounce him innocent.
At the time the text was written, this was designed to be a rhetorical question—you know, an "if only" moment. But in Christian theology, Jesus emerges as that mediator. To top it off, Job also cries, "For I know that my Redeemer lives" (19:25); it's easy to see how this can be interpreted as a proto-Christian exclamation.
Although there is no record of Jesus teaching Job, many people read Jesus' advice to turn the other cheek against violence (Matthew 5:39) as an extension of Job's realization that he must accept what the universe throws at him. In other words, Job learns that the only way to react to misery and violence is to acknowledge that he has no understanding of why or how it works.
Elihu's words in 33:23-28 are sometimes read as messianic, too. Elihu speaks of "a mediator" who would be "one of a thousand" (33:23). Early Christians must have read this passage and thought that they had found a link between their beliefs and the older law. Haven't you ever listened to an old song and thought it was talking about your life?
In Islam, Job is known as a prophet, and he has a place in the Qur'an, too. The Qur'an, though, focuses on Job's piety and his faithfulness, and gets rid of most of Job's discussions with his friends. Job was probably pretty thankful for that. But like in rabbinical literature, Islamic commentary and scholarship has focused on filling in the gaps to better understand Job's character, and a lot of discussion has come from it.