The prophet Jonah, son of Amittai, from Gath Hepher in Israel, prophesied sometime between 782BC & 741BC during the reign of King Jeroboam II of Israel (see 2 Kings 14:25).
The Book of Jonah is a story about Jonah set around this time, before the conquest of the northern kingdom of Israel by the Assyrians in 722BC, and before the Assyrian empire was defeated by the Babylonians in 612BC (see Israel falls & the exiles are led to Assyria).
It tells how Jonah - a Jew - is sent by God to the pagan city of Nineveh, the capital of Assyria, Israel’s worst enemy.
The Book of Jonah is quite unlike any other prophetic book of the Bible as it tells the story of a prophet who tries to disobey God’s command.
The reconstructed Nergal gate at Nineveh (JoAnn S. Makinano)
The story of Jonah can best be understood as an Old Testament parable (a story with a moral or religious meaning whose details aren't all literally true). It isn't always realised by readers that this form of teaching in parables was just as common in the 6th - 8th centuries BC as it was in the New Testament times of Jesus Christ.
Jesus wasn't the only Jewish rabbi to tell parables. It's interesting, for example, to compare the parable of Jonah (Jonah 1-4) with other Biblical parables in Ezekiel 15-17 ('The story of the Vine') and Matthew 21:28-22:14 ('The story of Two Sons', 'A story about God's Son' & 'The story of the Wedding Feast').
To understand where Jonah 'fits in' with the other Old Testament prophets (both historically & geographically), see The World of the Old Testament Prophets.
Two Assyrian archers at Nineveh
Jonah
Title? The Book of Jonah.
Written by whom? The author of the book is not identified. The story is about Jonah, son of Amittai.
When? It was probably written a few years before 722BC.
Where? Jonah was from Gath Hepher near Nazareth in the northern kingdom of Israel.
To whom? Jonah is sent by God to the people of Nineveh, the capital of Assyria.
What was the message? The real point of the story isn't about a mysterious fish rescuing Jonah; it's that God will forgive even the most wicked people if they repent and give up their evil ways.