I could never understand it myself. All Jonah did was to proclaim: "In just 40 days more, Nineveh will be overthrown." Not a single miracle, no display of supernatural power, nothing!
How the bloody hell is that supposed to be convincing???
And we are expected to believe that he was not harmed in any way by the bloodthirsty & barbaric Assyrians??? They allowed him to insult them before their very faces??? I'm certain that he would definitely have been put to death if this was an actual event...