One of my family members was reading a commentary on Jonah. The commentator gave following reasons why the Old Testament book of Jonah should be obviously considered a parable:
1. Chapter 3 verse 2 says that Nineveh "was an exceedingly great city of three days journey". The city has been excavated and shown to be three miles across.
2. The short sermon having such a great effect is obviously hyperbole (3:4).
3. The history of the region would have been much different had this event taken place.
I hold the Bible to be the inerrant Word of God. That does not mean there are not difficulties. To the first claim, I hold to the classic conservative position that the size is not a reference to the actual city walls but to the outlying areas too. I grew up in a rural area and we always said we were from Lebanon but in reality we were 15 miles from the city line. Right now I live in the Baltimore area, but in reality, I live in a suburb in the next county over. Do I live in Baltimore? The real answer is both yes and no. It just depends which direction the conversation is taking which is correct.
To the claim that the sermon was too short to have such a great effect. The ancient writers, not merely Biblical writers, generally summarized speeches. (I forget which ancient historian of wars explained how he summarized the speeches of the generals.) The message of John the Baptizer was not merely "Repent ye: for the kingdom of heaven is at hand". He had a few more things to say besides that is fairly obvious. But as a summation of his message it is accurate. In Act 2:40 the writer says "40 And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation." So the writer explains about Peter's sermon and we can conclude that he summarizes with the rest of the sermons also.
The final claim about the course of history being different sounds like the commentator is reading more into the "revival" than necessary. Of course there is some truth that Assyria was not a worshippers of the God of Israel. The repentance of Nineveh is apparently a short term thing that did not have lasting impact. A lot of the nationalism that followed 9-11 has grown cold. We are in the midst of war and people are taking our circumstances as common place. Sort of funny.