The following considerations provide explanation for this statement: first of all, the readers are given a unique perspective from which to evaluate the friends’ explanations for Job’s suffering, which appear from chapter three on. The friends move through almost the entire spectrum of possible explanations for the Job problem. Perhaps Job refuses to admit he has sinned, or he has sinned unconsciously. Perhaps he has to suffer because he—like all other human beings—is guilty by nature und must be educated in a certain manner. The friends argue back and forth within these possibilities. Job, however, rebels against all of these explanations, and the readers of the book know that he is right!
Job’s suffering cannot be explained by anything Job has done against God, nor is it the result of the fact that humans cannot be justified in the eyes of God. Even the idea of divine pedagogy is not correct. The reason for Job’s suffering lies solely in a cruel heavenly test, to which God and the satan have subjected Job. The prologue makes this absolutely clear.— Job's Journey, page 16
Sounds harsh, doesn't it? But it does make sense of the evidence...what does it say about the character of God, though? I'm wrestling with that...