Why doesn't God chastise Yona for disobeying him? Perek 3 of Yona picks up as if nothing had happened.
If Job is about how the ways of G-d's justice are beyond our understanding, then Jonah is about how the ways of G-d's mercy are sometimes beyond our understanding.
Jonah in fact expected G-d's vengeance -- according to Malbim, he went to the bottom of the ship figuring he would be killed by the storm, and tactically this way he would go quickly and the sailors on top would likely survive. Instead, G-d baffles him by opting for rehabilitation. The same pattern repeats itself with what happens to Nineveh.