Jonah 3:10 And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did it not.
Jonah 4:1 But it displeased Jonah exceedingly, and he was very angry.
I finally understand why Jonah was angry when God didn't blow Nineveh sky high. One reason was because 40 days before he had said that Nineveh would be destroyed for all of the wicked things that the people had done. So, he thought that they would call him a false prophet. When this is combined with the fact that the Assyrians had been very cruel to Israel, I can see that Jonah didn't just want them to be blown up because God had said so before. However if I were one of the citizens of Nineveh I don't think I'd be angry at someone because their prophecy of us all getting fried didn't come true, lol.
I also now understand more fully why God gave him some shade from the sun with gourd (or whatever it was) and then made it die. Jonah became very unhappy that the gourd had died; so God said that Jonah had taken pity on the gourd, so shouldn't he take pity on the over 120,000 people in Nineveh or who had just repented.
Anyway, just thought I'd write something about my new understandings of the story of Jonah.